Editing Join.php

The one problem I hate about the Admin Panels fields builder is the lack of an HTML block option.

I want to insert a description of member levels above my Join form. So I essentially Want to put an HTML block above my join form or in it.

Is there a way to do this in the fields builder of the Admin Panel? I have begun messing around with join.php, but Im not sure where to place my HTML block.

I'm a new user to dolphin so I'm still learning how to edit everything effectively.. If someone could help me I would really appreciate it.

So I simply need instructions on -How do I put an HTML block on my join form, above the form that described my various member levels and features

You could go to the Admin > settings > Builders > Fields Builder> Join Form and drag the description box to the left of Active Items which would place it at the top and load it up with whatever you want to say  ..... 
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That doesnt allow me to post an HTML block, it only allows a sentencr or two description..