Action Details
Requirements and how-to articles for Tumblr's action:

Post a video on Tumblr.

You need this to get it done:

File format: .mov or .mp4
Maximum file size: 100MB/5 minutes in length (daily limit)
Maximum width: 500 pixels
Maximum height: 700 pixels
(these restrictions do not apply to videos embedded from other websites)
Requirements missing or found errors? Report

How-To Articles
A list of useful links for you:

Tumblr Help Center - Video Posts
When you are logged in to Tumblr, navigate to the homepage (a.k.a. the "Dashboard") and at the top of the page next to your blog's avatar you should see a list of different types of media. Click "video" and then choose whether you wish to upload a video or embed one from another website such as YouTube or Vimeo.
Link missing here or found errors? Improve How-Tos