Why can't I make forms? It won't allow me to

'Create Form' button isn't an option

You have created your account through the invitation link and that is why you can only create forms for the main account. To create a form, simply click the main account's folder and click "Create Form" button. Here's a visual guide for you:

If you want to activate your own My Forms page and create your own form, you need to ask the main account to remove you as their sub-user. My Forms will be activated after, just simply create your form before going to ask them to add you as a sub-user again.