You have to attach an X1R-C receiver to the foot of the 430EX II to use it in the Godox 2.4 GHz radio system. The X2T is a dedicated transmitter unit and cannot be used as a receiver.

Ideally, I would recommend that you consider getting a Godox TT685-C or V860II-C speedlight instead to use as your off-camera speedlight. It's more expensive than the receiver, but more convenient and robust for off-camera flash setups (they have a built-in Godox transceiver unit so you don't have to attach anything to the feet). Also, unlike the X1R-C, the TT685-C and V860II-C, if firmware updated, can be used cross-brand with Godox transmitters for Nikon, Sony, Fuji, Olympus/Panasonic and Pentax. So if you ever leave the Canon fold, you can still use those speedlights as off-camera TTL flashes over radio; all you have to do is rebuy your transmitter. The X1R-C becomes a manual-only receiver if used cross-brand.