I had to do this again and was still sort of confused, here’s the full details of how to do it in one post:
Drag the folder containing Syphon.framework into xcode somewhere, such as src or addons.
Syphon.framework needs to be copied to Frameworks.
To do this, under Target, add a Copy Files Build Phase that copies to Frameworks.
Drag the Syphon.framework from the folder inside xcode into this phase.