If you have FTP credentials to the server, then you can achive this.
I have FTP username and password. What else do I need? I can also have the firm make changes. And what are the next steps?
1) FTP to your site in the server.
2) Navigate to the cthub****.csi file under _mm folder
3) Edit the file and make the value <allow_html_snippet_insertion value='true' />
This will enable the html snippet option for your site for that particular role.