How to wrap code around button

I am using Thrive Leads for getting opt in Forms.
I am trying to write a little shortcode around a button (media element per drag and drop) on the site.
My question is how can i write a little shortcode from Thrive Leads around that specific button?
If i switch to the standard layout editor in wordpress i do not have any source code to edit.. not in “normal” nor in “text” mode..

Do you have any advice?
Thanks!