To automatically add donors who give to the Capital Fund to the Capital Campaign:

Enable Automatic Campaign Member Management in NPSP Settings: This feature allows automatic management of Campaign Members based on criteria defined in NPSP settings.

Populate the Primary Campaign Source Field on the Opportunity Record: By setting the Primary Campaign Source on the Opportunity record, donors can be automatically added to the associated Campaign.

These steps ensure that any donor contributing to the Capital Fund is automatically linked to the Capital Campaign, streamlining the process and ensuring accurate tracking.