Cannot edit files through my WP dashboard

I am using Academia WordPress theme by WPZoom.

I tried to remove the Powered by wordpress theme Academia link in the footer. I checked the WPZoom website and there is permission, if I want to remove the link I can easily remove it, but to my surprise, I don’t have the editor to edit any of the files on my wordpress dashboard, how is this possible?

When I click on appearance, I have everything else except editor, this means I cannot edit any of the CSS or PHP files.

Does someone know what to do please help.