How to Change Installs

I have apparently made a horrible, terrible mistake. My new host has a softaculous install helping thing, which included WordPress. Typically, I’ve done my own installations. However, I thought it might be faster and more convenient to use softaculous. I honestly thought it would do a full install of WordPress. I appear to have been wrong. As I log into my wordpress administration, I go to the theme section to see about adding a new one and there’s no button to “add theme.”

How do I go about reversing this without undoing anything I’ve done so far. Is there a way to re-do the install or do I need to scrap it and start all over?