Just to make sure, that I understood right: You have hardware with an installed UCS and connected a Wifi USB adapter to the hardware. Now you want to connect to WLan via the USB Wlan stick as a networkcard.
I think you first would need to make sure, that the USB Stick is properly acknowledged and the acknowledged as a network adapter. So: is the WLan USB networkcard acknowledged in UCS (does UCS “know” it has a networkcard)? Second you need some way to use the WLan stick to discover WLans and connect to them - I do not know if UCS has that abilty out-of-the-box but there should be tools that let you do that.
Though, I would recommend to connect via networkcable.
You’ll find the wireless-tools and wpasupplicant packages in UCS. With those you should be able to connect to a wifi network. There is no graphical support for this, but there are a lot of how-tos on the internet. To check if your network card is supported, read the output of dmesg and run ifconfig -a. You may have to install a fireware-package. You’ll find the name of your network card using lspci.
There is good support in Debian 12 for wifi adapters - even non free drivers.
I have an rather old laptop running Atheros AR9485 wifi I installed UCS on for testing.