How to prepare for RAGBRAI

So recently I decided that I want to participate in RAGBRAI this summer. The wiki from this sub answered my questions about what kind of bike I would need but I couldn't find any information on how to train for this kind of ride. Google has some programs but they don't seem to come close to the kind of distances at RAGBRAI. Other subreddits like r/fitness have a list of their goto programs to help beginners get into different sports but I haven’t been able to find something like that here. I’m looking for some kind of program to follow or at least some guidance on how to prepare myself for RAGBRAI.