Creating a new flex tab button and adding content

Hi!

I hope someone is willing to help us out with this.

We are looking to add a button or two more into the flex tab however we want to add iframe codes and/or HTML5 codes into it.

Could someone please direct us in the right direction how to do that? We’ve found the flex tab file however no idea where to go from there since most of that file is just API calls.

Thank you!