If you go with a team they will take you to the start usually from a staging town they meet at in Iowa. And they return to the same town. If you fly in find a team near Des Moines for the best air service although there are some other towns that work well also. If you’re driving make sure the team has week long parking available. A team is also a good social circle for the week.
If you are looking for a team to ride RAGBRAI with it is not too late. Look for Iowa based teams on this forum after March 31st. There are usually plenty looking to fill spots as some of their riders drop out. You don’t have to register with a team to go with one.
The other option is to use one of the charter services listed on this website. They always have arrangements for people flying in to RAGBRAI.