To use Printed Simply with Customily for Shopify or WooCommerce, the first thing you need to do is to create an account on Printed Simply. If you don't have an account with Printed Simply, you can create one here.

Once you have your Printed Simply account created, open your Customily app on Shopify and follow these steps.

1. Head on to Start or Store on the left menu
2. Go to Settings and open the Integrations tab.
3. If you have more than one store on your account, make sure you are changing the setting of the correct store by selecting it from the top left dropdown.
   
4. Select Printed Simply from the Select a provider for integration dropdown
5. Click enable integration
   
6. Paste your Printed Simply API Key (also known as Customer Identifier). Learn where you can find your API Key on Printed Simply here.
   
7. Click Save Settings at the bottom of the page.