How can I enforce the terms of a trust and get a distribution?

As a beneificary?  Follow the rules set forth in the trust, if any, about making a demand upon the trustee to perform.  If that fails, you would need to file a petition with the orphans court setting forth the terms of the trust, your rights, and why you areentitled to recovery.  Trust litigation can be complicated and the rules of procedure in Orphan's Court difficult to understand.  You will have your best chance of success if you retain experienced counsel to assist you.  The trust might even be required to pay your attorney fees.