Go to your Account Settings and click Edit Appearance. Then select Edit Theme.
Underneath Custom Theme, click Edit HTML.
Copy and Paste Script
Paste the POWr script into the HTML file between the Head tags. Update, then save.
New Text Post
Back inside the Tumblr editor, insert a new Text Element.
Copy and Paste Shortcode
Paste the POWr shortcode into the text post, then save Expand the post to see your new Social Stream plugin. Click the Settings Icon to launch the POWr Editor.
To edit your Social Stream on Tumblr:
Visit your live Tumblr website and select the gear icon in the upper right corner of your Social Stream Plugin.