Family Historian User Group

My wife was adopted at birth, quite late in life she decided to find her birth mother. As a result I now have her birth certificate and have used AS to create a source for her birth with her certificate image attached.

I now want to create a source for her adoption. "Adoption" doesn't appear as one of the Source Types in AS, but an adoption certificate is basically a birth certificate with the name changed. Can I modify the AS Birth Template to create this source?

No, because the Birth Event is quite different from an Adoption Event.
AS is only intended to capture the more popular Census, Birth, Baptism, Marriage, Death & Burial records.
All other facts and source citations should be entered directly into FH.
In this case, use the standard Adoption Event and add Source Citations along the same lines as AS would for both the adopted child and the adoptive parents.