Many family site members help Site Managers work on the tree by adding names and photos from their side of the family. That way Site Managers can grow their tree and family site members can make sure the information on their side of the tree is up to date.
However, allowing members to edit the tree is at the discretion of the Site Manager. The Site Manager can configure settings to allow or disallow editing the family tree for family site members.
Family trees that were created on a MyHeritage family site, either by importing a GEDCOM file or starting the tree from scratch directly on the site can be edited by the family site manager and also the family site members by default.
If the tree on your family site was synced from Family Tree Builder, by default it can be edited online by the original site creator only, and it will remain read-only for other site members.
If you aren’t able to edit the family tree on your family site, please check with your family site manager.