How can I change the "Founded by" to another person?

Answer 1

You can't change the "founded by" person in the current family tree, but you can export your family tree and import it as a new tree and set a new founding person. Note that pictures are not exported.

The only way I know to fix this is to create a copy of your tree as follows:

1. Export a GEDCOM backup of your tree by clicking "Download / export this family..." at the bottom of the left sidebar. 
2. Choose GEDCOM and click download (note where you save it).
3. Click on "My Account" at the upper right of screen.
4. Click on the "Create or import new family" button.
5. Click on the "Import GEDCOM or FamilyScript..." botton at the bottom of the left sidebar.
6. Browse and open the GEDCOM backup you made. Click "Import".
7. Find the person you want to use as the "Founded by" person. Note that this is also the person you will go to when you click "back to me".
8. Click on "Finish Import"

You should now have a copy of your tree with the corrected "me" and you can go to the My Account screen and delete the old version and rename the new tree as desired. Again, note that pictures are not exported.