New landlord - should I accept a renter with cosigning?

Hi Guys, I am trying to fill in a 1 bedroom apartment in a duplex (Lincoln, Nebraska). Some of the applicants I have are students without much of a credit history. when the parents are willing to cosign, whats the procedure to do this? Do I need to add them to the lease? or do they fill out a seperate form?  I know I need to screen the parents too. I am sure some of you would have done this before. Please guide me if you could on the legal way to do this. 

Appreciate your time!

Thank you,

Kar