Creating New Custom Entity Record when Opportunity is Won

Hello

I have added a workflow to my opportunity entity to automatically create a new custom entity record and pull over details from the opportunity.

There are a couple of other field types I am not sure how to correctly put into the newly created record:

Option Sets:- I want to copy the same data in the opportunity to the custom entity (both use the same option set)

Stake Holders:- I have stake holders created on the opportunity but want to also add these to the custom entity - is this possible?

Thank you

Robin