Before you get to the point of uploading it might be worth thinking about whether you want to follow a 'track' or a 'route'. The former is a passive but fairly clear magenta line on the map, you control the level of detail by zooming in/out (this is where the 10,000 trackpoint limitation comes in). Routes give you turn by turn directions, beep alerts, autozooming and big white arrows at junctions (this is limited to 50 waypoints and also needs to be split between out and back on a circular route). After some trialling of routing I now favour tracks because it's reliable and because it takes you exactly along the plotted track rather than thinking for itself and taking you where it thinks is the best 'route' between two waypoints.
I would suggest downloading Basecamp. My workflow is usually. Plot route in RWGPS, export as a GPX, open a new 'list' in basecamp, import GPX, this will appear as a track, check it doesn't exceed 10,000 points (if it does use the filter to downsize or split), split the track if there is any confusion between out and back or if it's easier to mark out the stages of an audax and ensure that you don't miss a control, rename all the tracks (part 1 ... etc). If you wanted to this is where you could convert the track to a route and limit it to 50 waypoints, I don't do this but my understanding is that it's crucial to get the location of your waypoints right. Then with Etrex plugged in as a spearate drive and the 'list' in basecamp highlighted, click the send to device button. Then as Frankie explained, dismount the etrex, use the 'where to' and choose tracks or routes and you should see what you've loaded on to the unit.
In terms of using, saving etc. At the start of a ride I go from the data screen to menu and clear the track and the associated data, there is now one selection that does both. Load the track and go. At the end I always go to the track manager on the main menu and save the current track. Connect to the PC and find the saved track and then do a manual upload to Connect, Strava or RWGPS.