Just get on the bike and take it easy. How long you go is up to you, but try not to get yourself too winded - take fice if you start getting close, or just coast along for a bit. Don't hesitate to walk hills if you feel you need to until you get in better shape.
A bike path is a good first ride, even though you have to deal with unpredictable pedestrians. Learning how to deal with traffic can come later when you're more comfortable riding.
If you're not having fun, you're not doing it right and need to keep biking until you get it right.
