To share a publication to Tumblr, make sure you are logged into your Tumblr account, so you can skip the login process when sharing. You can also share without being logged into you Tumblr account, but that will generate an additional step for you during the sharing process.
See the GIF below or skip to the written instructions after the GIF.
1. Click on "Share" underneath the publication you want to share and select the Tumblr icon.
2. Click on the icon to share, and you'll see a dialog box pop up, where you can edit the caption that goes with the publication you are about to share, change style options and even edit the HTML for the post. You can also set advanced options such as when to publish, tags to use for the post, as well as the publishing date, by clicking on the gear icon.
3. Click on "Post" to share to your Tumblr account and you'll see a sharing confirmation window. Now, as an added step, you can check on your Tumblr account to see how the shared publication displays on your Tumblr site!