Here is an example of adding (moving) a WiFi adapter from host and into a system container.
incus config device add mycontainer wifi nic nictype=physical parent=wlx000f007ce055 name=wlan0
You should specify the nictype=physical, which adapter name on the host you are moving (parent=wlx000f007ce055) and perhaps what interface name it should have in the system container (name=wlan0). For the last part, if you do name=eth0, you would be masking any other default network interface with the same name.