How is Resource linked to Project?

Hi,

Sorry for the vague question. I am doing support for a customer who is having problems with a custom concurrent request. There is limited documentation on site hence I am checking here.

We know the problem is to do with the resource assigned to the Project. If we go to Project Status Inquiry for the Project, there is a "Resource Status" button:

Click "Resource Status":

I can see that a project is linked to a Resource via the PA_RESOURCE_ASSIGNMENTS table, but I can't see where I go to link the Project to a Resource.

There are no options on the actual project: