Hmmm. I was sort of hoping that using GPS was not going to be a geek fest. 
So, I need to learn how to use bikehike, install and learn how to use mapsource, then I can do something. Surely there must be a more straightforward approach?
<daunted and put off by the complexity >
All the above posters have put forward excellent procedures, but like you suggest you are, I am technically challenged in GPS (as in so many other ways!)
I too started with a Map60CSx and Mapsource but after I discovered that the "autorouting" function in Garmin is not sufficiently reliable, in my opinion, I got into the habit of simply using Tracks.
You may have already discovered that Routes are a series of marks between which the GPS unit navigates according to a path of its own choosing; if you set it to "Follow Road" it will (mostly) take a path which conforms to the mapping contained in the unit. I say "mostly" because it will occasionally decide to "avoid a Highway" (if you have set it to do so and you do need to do this to avoid really major roads) typically when your preferred course takes you across a staggered crossroads of a major road; it then looks for a 90 degree crossroads of the major road and may go miles looking for one! Since the GPS unit uses different programming to the mapping software the path it will calculate may not agree with the path the mapping software generates on your PC screen.
The knowledgeable ones amongst us (see above) have ways of minimising this nuisance, usually I think involving the intelligent placing of extra waypoints, but I didn't learn this until after I'd become accustomed to using Tracks.
Tracks are lines you draw manually on whichever software you are using and transfer as such to the Map60; the unit doesn't do any work on them, it just displays them. You just watch the screen and make sure that the position arrow follows the line. In truth, you don't even need maps on the unit although this does make interpreting junctions in advance much easier when in motion on the bike. It's handy though if as occasionally happens, the unit "loses sight of" its map - the line is still there as a sort of back-up. You can also display more than one Track at a time, in different colours, so if there are options you want available when at that point in the ride - say, "shall I go short and hilly or long and flat?" this is easy to do (I admit however, that if you are using a Route, you can still display the option as a separate Track and achieve the same result.)
If you presently have no mapping software on your home PC (i.e. you don't have Mapsource or Memory Map, Anquet, etc.) I would not rush to buy any just yet. I bought Mapsource years ago when I got my Map60 and found I desired OS mapping on screen so much I subsequently bought Memory Map and now use that almost exclusively, so I don't have much experience using on-line mapping. At the time I made these investments, my Broadband was so crap, I couldn't rely on the on-line stuff either, and this would still be a factor in my decision if I were starting again, since my desktop Memory Map is so much smoother and faster than on-line stuff. But things are changing fast and the free on-line stuff is much improved. You should get the advice of others more skilled in this area, but I have noticed this, which I think looks interesting for example:
https://yacf.co.uk/forum/index.php?topic=45801.0 although I haven't explored it enough yet to know.
I'd recommend you play around with Tracks versus Routes first to see which you like best. The Track has the advantage of cluttering the screen less; I found that the pop up instructions would often obscure the map just when I was trying to interpret it, at a complex junction say, and for me, it's easier just to read the map as if it was an conventional paper one; I even use it in North Up rather than the car satnav style of Track Up where the map swings around as you turn. I admit I may be the minority here but you should try-before-you-buy as with all the options! I suspect using Tracks consumes less power too than using Route navigation, so that's another plus in my book if I don't have to change batteries so often, although that's really a matter of self- organisation: change in advance at Controls, for example.
Composing a Track on your PC may seem a bit tedious but I have found that with a little practice, it's fairly quick and it has the merit of being simple. I find it also very helpful to review the journey to gain some familiarity before the ride and this follows naturally if you're drawing a line to follow.
As a P.S. - the Map60 is a heavy lump, especially with non lithium batteries (Energizer Lithiums are the best of the diposables, in my experience) so make sure the bike mount is firm. Put some Vaseline or similar on the lugs between the cradle and the bar mount - there will be movement here and the lugs grind away and snap - if you see white dust, this is happening. Also, always attach a lanyard as a back up. Be aware that the Map60 has a reputation for shutting down if subjected to heavy vibration; typically, when hammering downhill over rough surfaced Tarmac; it helps if it's not mounted horizontal but angled slightly up at the front; if it's dead flat, it tends to rock rapidly back and forth and it really doesn't like this!
In other respects, the Map60 is a great unit - good reception, easy buttons even with winter gloves, fair sized, legible screen, widely customisable. Enjoy!
