Go read the stickies in the road racing sub forum. Several on getting started. Find a local group/shop ride and try it. Enter a few local races and get to know some of the locals. You can ride without being a member of a team while you figure out if this is something you want to pursue. Friel, Carmichael, and many others have books & websites with training programs.

Many of the races will be criteriums (crits) - multiple laps around a smallish course, often several corners, lots of accelerations, riding full-out in a pack. Different fitness and skill set vs. the bike part of a triathalon. OTOH, a time trial will be just like a tri.