There are 2 options:
First you can set or disable all css for a regular popup.
The second option is to open a classic pop-up or modal dialog by clicking a button or clicking on a specified element in the editor. When you close the popup, you can write something back to the editor using a command like
tinyMCE.get("my_editor_id").execCommand("mceInsertContent",false,'whatever');
source share