You have to apply on the forum directly by opening a new proposal under
“Proejct name - UCG Proposal” title and select “Governance” & “dApp Staking Applications” categories
It is a similare process to dApp staking proposal for which you have to describe the projet, team, target etc… as you’ve already did for your dApp application.
You can also inspire yourself of other UCG application on the forum. You can find them easly by searching for “UGC application” in the reaserch box 
you can find here a bit of information on UCG here :