Destails Content Inside Free Membership Option How Do I Do That?

I think I am having a thick moment and yet I can't seem to see where I am able to do this.

I am only running Member with a free Member level and when I hit the register page I have the typical grey box with title and sign up button.

That is all fine yet I want to put content inside that box to sell the sign up.

How do I do that?

At the moment it is looking bland.

I found another thread where someone had a great example of content inside this box and have attached my what i have and what i want graphic to help people understand what i mean.

Thanks
Chris