It's quick and easy to link your Shopify account when setting up your account. When signing up or on the activate section of the website, under the Platform Selection, choose Shopify:
Then you will be prompted to connect your store. Do not worry this will take you to another tab where you can complete the activation. Once you're on the screen pictured below just enter the URL for the Shopify store you want to connect!
If you are not already logged into the store then you'll be prompted to log into your Shopify Store. You may not see this step if you are already logged into your store!
Once you enter your Store URL and have logged in then you'll be navigated to your orders page where you'll see each of your orders ready to ship!
If you go to the settings tab on the left panel of your dashboard and click on the integration tab and you should see that your store has been connected.
