answer:So, go to your tumblr blog, then on the top right next to “Dashboard” there is “Customize”. Click that, then it’ll take you to a page with a few options up top, and a preview of your theme. Click “Theme” on top (second option in from left to right), and a window drops down showing a bunch of themes. At the bottom of that window will be a “Use Custom HTML” option. My tumblr if you’re interested: James’ Tumblr