[Urgent help required] Problem with putting a custom field in a page (AURENA)

hi, my goal is to put Project ID dropdown list from Project Definition Page into Business Opportunity.

I’ve tried with some manuals from IFS but it’s very hard for me to figure out without step by step tutorial. I’m very new to IFS.

My question is,

1. In the Active Page, Datasource Entity Set already exists with BusinessOpportunities, how can I put different data source (Project Definition) here?

2. I’ve created Entity Configuration, Projection Configuration but I don’t know how to plug them in to get Project Definition in the Page Design.