Copilot Studio with GPT-4 (Turbo too)

Hello - we have been working with Copilot Studio and cannot find documentation about how to connect it to GPT-4 etc. We need the fullness of GPT-4 (V, Turbo etc.) for our use cases. 

Note we were able to build a POC for a client using Azure AI Studio and GPT-4 32k. We just can't seem to do this in Copilot Studio. I think it's using some other model (not even GPT 3.5 Turbo). 

Thanks in advance!