In the Bigcommerce app marketplace locate the Shiptheory app:
Click the Shiptheory app and click Install:
This will then show you a confirmation page. Once you are ready, click Confirm:
If you are currently not logged into Shiptheory or don't have an account you can either sign in or create an account and sign in:
You'll then be directed to the activation settings. Here you can specify when you process orders, e.g. when a status update will trigger the shipments being sent over to Shiptheory:
Once selected, click Activate:
You will then be directed to your settings where you can specify on which status you want Shiptheory to process orders:
When you're done, click Save.