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

Requirements
You need this to get it done:

Set up Google Analytics Account
Create a Google Analytics account to start being able to use it to track your blog's traffic.
Add Google Analytics to Your Tumblr Blog
Add your Google Analytics ID to your blog's theme.
Requirements missing or found errors? Report

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

0
Tumblr Help Center - Google Analytics
How to use Google Analytics with your Tumblr blog.
Official
0
Google Support - Get Started with Google Analytics
How to start using Google Analytics.
Official
Link missing here or found errors? Improve How-Tos