Budget - How to add FF information after making the reservation

Is there a way to add FF information to a Budget rental after making a reservation but before it has started? I have a reservation using my corporate travel portal but it didn't have any place to add the FF information.

I also went on budget.com and pulled up the reservation but couldn't find a place to enter my FF information.

Thanks!

There is nowhere to add your FFN, i always have to remember to add it when I get to the rental counter.

You need to have a RapidRez account number to login and make your reservation. In the step 4 of 4: rent it!, you will be able to choose frequent flyer program and enter the number.