When creating a delivery you'll need to test it and receive a success response in order to move it from Saved > Inactive/Active.

To do this, fill in the requirements and sample values on the delivery and hit the "Test" button at the bottom of the screen here:

When you get "Response matched expected response" you can hit "Save".

Don't forget that you'll need to include your success response in the "Remote System Response" section.

Once completed it's as simple as selecting "Enable" or "Disable" to change the status of your delivery: