USB Wifi is currently not supported at all and it may still take a long time until it works.
There are plans to support it one day,but I don’t know at which position of the To-Do list it currently is,you should expect at least some months.
If your computer has a Ethernet port,then you can use a Ethernet Wifi bridge.
It looks like a normal Ethernet cable for Haiku and the Wifi connection is configured using a web interface.
I have this one and can 100% recommend it: WiFi-Bridge Vonets VAP11G WLAN Adapter | Kaufland.de
It works great for my Haiku computer where the built-in Wifi isn’t supported (it’s PCI but still not all cards work…)