How to edit in designer mode with CMS site plan?

Hello! The company I work with subscribed to the “CMS site plan” (hosting plan) and we didn’t get a account plan. I thought I could edit and design in the “design mode” with this plan. But I can’t reach the design mode. How do I do it? Do I have to subscribe to another plan?

I only have access to this edit mode:

Here is my site Read-Only: LINK
(how to share your site Read-Only link)