Customise Help Centre footer

Customise Help Centre footer

Since it's still not possible to have SSO and link my users to the KB, I'm trying to customise the footer in the KB so that the SUBMIT A TICKET button links to my site where they can contact us. (When they do this certain user information is also added to the ticket before it's passed on to the help desk.)

Where can we customise the footer to change the destination of the SUBMIT A TICKET button?

Thanks.