How to allow currency other than XRP through XUMM Wallet?

Hey there,
So we have successfully integrated XUMM to create our first version of the NFT marketplace app. We only support XRP right now, but we would like to expand this to allow alternative XRPL-issued tokens like XGBL for example. But we can't seem to figure out how to do so. Let's say I have another 50 XGBL tokens in my wallet. How can I use that token instead of XRP while I buy NFT through a transaction performed by XUMM.

Thanks for all the help!