He made it kind of tricky, but here's a relatively easy way to do it:
Open your AdminCP
Go to Themes section
Enable "Designers' Mode"
Make note of your theme's ID number:
On your Web Server/File Manager/Console, navigate to: "PATH/TO/ips_suite/themes/3/resources/core/front/custom/"
Open/Edit "ta.libary.js" and search for:
ta_c.innerHTML="Theme by Taman",ta_c.setAttribute("href","https://invisionpower.com/profile/537452-taman/")
Note: See the text "Theme by Taman" and the URL "https://invisionpower.com/profile/537452-taman/ "?
Remove the "Theme by Taman" text and the URL:
ta_c.innerHTML="",ta_c.setAttribute("href","")
Note: If you have Notepad++ (or similar text editor), you can use the find and replace feature to "find" the unedited line, and "replace" with the edited line above.
Save/Upload
Disable "Designers' Mode"
Go to the Support section in your AdminCP, select "Something isn't working correctly" and click Continue
Congratulations, you're done!