3rd party Wiimotes are hit or miss with Dolphin: some work, some don't. Attached extensions should be automatically detected as long as your Wiimote is connected and "Real Wiimote" is selected in Dolphin config. You could also try booting the game with the accessory already plugged or pressing Alt+F5 sometimes while the game is running..
Avell A70 MOB: Core i7-11800H, GeForce RTX 3060, 16 GB DDR4-3200, Windows 11 (Insider Preview)
ASRock Z97M OC Formula: Pentium G3258, GeForce GT 440, 16 GB DDR3-1600, Windows 10 (22H2)
ASRock Z97M OC Formula: Pentium G3258, GeForce GT 440, 16 GB DDR3-1600, Windows 10 (22H2)