Click on Manage private App located at the bottom of the Apps page
You may need to enable Private Apps. In case you do, you'll see a screenshot similar to the below. Simply Click Enable private app development. You can follow instructions here to enable
Click Create new private app, to create the private app
In the Admin API section set the following: Products: Read access Script tags: Read and Write access Store Content: Read and Write Access Themes: Read and Write access
Set Webhook API version to the latest version.
Click Save when done and then click Create app when the modal window appears.