Once you’ve selected the options you want, click Continue on the bottom of the page.
Alternately, if you’re logged into Tumblr, simply browse toTumblr.com/customize.
On the Customize page, go for the Appearance tab.
Scroll down to the bottom of that list, and paste your Disqus shortname in the Disqus shortname box.
Remember, this is the shortname you entered when you were signing up for Disqus.
You may see different options depending on your theme, but most themes will include a Disqus options box.
Once you’re done, click Save + Close in the top right corner.
Now, in a separate window or tab, open your Disqus instructions page we mentioned earlier.
If you don’t have it open, browse to the Disqus Tumblr installation page (link below).
Once you’re there, copy the text in the box under Manual Instructions part 2.