not that most of don't think that way? Right?
There are a number of resources on the internet but I've found them to be overwhelming and confusing to the novice. Since you have stated you've joined a team, I imagine there is a team captain/leader, ie; someone who is experienced at cycling and distance. Since you can ride 8 miles, build on that. As others have stated, fit is the most important compenent. What I do know about road RIDES is that there are a number of rest stops and I would recommend you to avail each one. Get off the saddle and walk around. Riding in a group for 32 miles is a whole other beast, so I am hoping your team leader will set up some training rides with other team members. Ask questions from your source/contact...I am fairly certain all these things will be addressed. Also remember to dress in layers, as you can take off as you warm up. As Ironz stated, I train by hours...not distance. Some are easy, some are hard, some are inbetween. Back last August, I did an olympic distance tri and my bike speed average was 21mph on a fitted tri bike. Right now I am ramping down from long endurance rides and starting to work on shorter, faster intervals. I've got 2 months to prepare myself and so far so good...