In the Tumblr Editor, open your Account Settings and select Edit Appearance.
On the next page, select Edit Theme.
Click on the Edit HTML link.
Paste this exact script into your Tumblr HTML file. It's best to add it between the Head tags. Then click on Update, and save.
Create Text Post
Return to your Tumblr Admin page, and create a new Text post.
Paste this shortcode into the post and save. If you expand the post, you will see your new POWr Event Gallery. Click the POWr Settings Icon to set up POWr Event Gallery.
Edit your Event Gallery on Tumblr:
Go to your live Tumblr website and click the settings gear in the top right corner of the Event Gallery Plugin.