Dilan
To do this, you can open the page you are working on using a microflow and set the association in the microflow before opening the page. I'll assume you are creating a page for the Supervisor_Funds entity. In the event that you are creating a new Supervisor_Funds object, you could create a microflow that looks like this:
The Supervisor_Funds_Edit page would look like this:
And on a datagrid page listing all supervisor funds, you could call this microflow with an action button:
If you want to see the microflow, you'll find it in this Model Share:
https://modelshare.mendix.com/models/2b71f0eb-84ae-4477-aaad-0917bc52485a/create-new-supervisor-funds
Hope that helps,
Mike