If you edit your tree online, please read the following article: How can I edit a fact in my online tree?
To edit a fact in Family Tree Builder:
Click the ‘Edit’ button and choose ‘Edit details [name of person]‘.
Click on the Facts tab.
Highlight the fact you want to edit.
Click on the ‘Edit Fact’ button and edit any of the fields.
Click ‘OK’ and ‘OK’ to save.