I am Makarand P from the Dell Social Media and Communities team.
With regards to your issue, i feel you might have the html text in word document or notepad and hence not getting the option of html editor. Save the document as .html and then try to select all and then you should get options for html editor. Else pasting the text in html editor software like Dreamweaver should give you options of html editor.
Kindly revert for further clarifications,
Thanks and regards,
Dell Social Media Responder