Hey Mate,
Prepare a covering letter and mention that you are sending them missing form now. Cover letter should contain all your personal details (Name, DOB, Address, Contact Number, Passport Number, Date of original application received and who received it).
Alternatively send them and email (scanned copy of cover letter and wife's filled form) from your email address that you have mentioned in application form. Ask them to confirm that they have put additional form that you are sending them with your original application.
I sent some additional documents too, and alternatively sent email as well. They replied to my email exactly after 31 working days confirming that the additional document has been attached to original application received and that they will consider this when evaluating my application.
Good luck