I could not believe there was no way to plan a route on a computer then send it to your phone and hit navigate. But i searched and searched and couldn't find it.
Well I finally did. This
site explains it best. Getting OsmAnd set up can be a bit confusing, but i was able to stumble my way through it. Also, you'll most likely have to connect your phone to your computer, go into the hard drive or memory card (mine doesn't have a card), open the OsmAnd Folder, and create the Tracks folder.
It is also helpful to have Dropbox or something and a File Manager program for you phone (i just downloaded the Astro App). This way you can export the gpx file to your drop box, open the filemanager app on the phone, and move the file from your drop box to the osmand\tracks folder without having to connect to a computer.
Another great tool is Furkot.com. It is still being developed but really good for trip planning plus it has an import/export function... so you can do a route in google maps (easier to see your directions step by step and make sure it doesn't have you swimming across the atlantic or something), export it using the gps converter, then import it to furkot which will help you plan out lodging and travel stats easier.
I have been trying to find out how to do this for so long. So I hope it isn't old news and is helpful to some of you!