Ak+Tk

You apply thru here . . . if you are in Milwaukee.
 
https://www.cgichicago.gov.in/index.php?/page/display/12/11
 
you might also be eligible for Visa on Arrival.

Does he have an american passport?

My husband immigrated from India in 2010 and became neutralized citizen in 2014. 
 
Now he would like to visit india. This will be his first time as a US citizen traveling back to India. 
 
We need help with his visa. I feel like there is not a clear cut answer on where to apply or an application link. 
 
Please let us know how to go about this. 
 
Thanks 

Just sign the I-485, put it back in the envelope with a copy of the notice you received, and mail it back. I don't think you need to do a new form...maybe just a post it note by the signature showing you have done it.