Can someone point me in the right direction? To set up a step sequencer Audio unit extension app, do i use the Apple provided MIDI Processor AU extension Template? And if so how would I access it via GarageBand?

Ive Just built a AUV3 MIDI Processor app, using Apple template for (AudioUnit extension app) The AUV3 instance is not appearing in GarageBand while using iPhone, iPad and m1 Mac mini. Using Xcode 14.2 If I create a AUV3 Instrument, the instance works fine and I can find it. Any ideas ? thanks