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. Update, then 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 to see your new Payment Form plugin. You can edit POWr Payment Form by clicking the POWr Settings Icon in the corner.
Begin customizing this Payment Form Plugin directly inside of your Tumblr website:
Go to your live Tumblr web page and click the gear icon in the upper right corner of your Payment Form Plugin.