Originally Posted by Bald Paul

You can plan out a route on Garmin Connect on your home computer, and then just "Send To Device" (your 830) with Garmin Express.

Originally Posted by rm -rf

on ridewithgps: draw a route. save it, giving it a title.
View the route and click Export Fit File, to save the route as a .fit file.

There are ways to auto update routes to the 830. But the simplest upload method is this (which I use). Directions for Windows PCs:
connect the Garmin to your computer via USB.
wait for it to boot up. Now the Garmin shows up as a USB drive.
In the Downloads folder, copy the route .fit file
Navigate to the Garmin device, then down to folder Garmin --> NewFiles.
paste the .fit file into the NewFiles folder.

I right click the Garmin device and choose Eject. This might not be too critical anymore, but it's still a good idea.

unplug the Garmin, boot it up. The route shows up in Navigate --> Saved Courses.

It will warn you of turns when you are close, with a popup map, even if the routing map isn't displayed.

Originally Posted by mibike

If your pair your Garmin and RideWithGPS accounts and Pin a route it will transfer to your Garmin. Pin the route in RWGPS and the next time your Garmin syncs with Garmin Connect on your phone it will transfer. If a route is already pined unpin it and pin it again and it will transfer.

Originally Posted by njkayaker

So, you use RWGPS to plan routes and you use the RWGPS app on you phone to navigate?

It's easy to transfer routes in RWGPS to your 830 and have it show the turns. This is what RWGPS started out doing over ten years ago (before they had an app).

People above have mentioned some options.

You can also install apps on your 830 (like on a phone) to download routes form RWGPS direcly. RWGPS has its own app and the GRouteLoader app does the same thing (as well as other stuff).
By the way, you are making a "route" or a "course" (or even a "track"). The "map" is the image with all the roads (and you aren't making that).