I am a cohost @Rica11 and when the host sets up my payment all they need to do is put in the % we agree for my services and the payment automatically comes through to the bank account set up on my profile.
When I looked at one of your listings though, you seem to be added as the cohost rather than the main host. If you are the owner but are listed as a cohost this will be why you can't add a cohost to the listing.