Tumblr 101, Lesson 5: Installing the Bookmarklet.
Click Goodies at the top of the page, and drag the ‘Share on Tumblr’ link to the bar. Once installed, a quick tap while you’re reading an article will pop up a small window offering Tumblr’s 6 standard post types. Now, if you find a great quote in the article you’re reading or a stunning photo, click the appropriate tab to share. The photo tab is reasonably smart, and will usually let you choose from all of the images on the page you’re currently browsing.
We’ve got more tips and tricks for building your Tumblr site at HuffPost Tech.