How to add a cosigner

[Mark Smith]

I'll try to keep this story short: I'm currently processing an applicant who is separating from her husband.  They are still friendly with each other, and the husband seems to want to help as much as possible.  As the wife does not have enough income to qualify for the unit, the husband has agreed to cosign.  How does this work?  Is it an extra paragraph in the lease and I have his signature on the lease?  Is it an entirely separate form?  Any advice or examples would be greatly appreciated!