Go to Account Settings Edit Appearance Edit Theme.
Click on the Edit HTML link underneath Custom Theme.
Paste POWr Script
Paste this exact POWr script into your HTML file, in between the Head tags. Once you add the script, click Update and save.
Create New Text Post
Go back to the Tumblr dashboard and add a new Text post.
Paste the Shortcode
Paste the shortcode into the post. Then save. Expand the post, and you'll see your new Twitter Feed plugin. You can edit POWr Twitter Feed by clicking the POWr Settings Icon in the corner.
Begin editing this Twitter Feed Plugin right in your Tumblr site:
Go to the live Tumblr web page and select the gear icon in the top right corner of the Twitter Feed Plugin.