Note: This can only be done in parts where the WYSIWYG editor is available. Not all parts allow the editing of direct HTML.

Versions 6.10 and Before: On Parts and Layout at the bottom left of the part \ layout pop up window there is a button that reads "HTML"  Upon clicking this button Raw HTML text can be edited and reconfigured.

Versions 6.15 to 6.45: In the tool menu on the parts \ layout pop up window there is a square button the reads "HTML" accessing this button will give you the ability to edit and reconfigure raw HTML data.

Version 6.45 and later: On the tool menu, click on the View tab, then click on the Code/HTML button. This will present a pop-up window where you can edit the HTML code of the part.