Click on Channels -> Add New Channel menu at the left menu bar.
Select the type Shopify from the left tabs as shown below.
Enter myshopify URL of your Shopify store and click on the button Save.
You will be redirected to Shopify for your authorization to connect your Shopify store. Enter your Shopify login to continue.
Now click on Install app button to accept the permissions.
You will be redirected back to the SKUBubble once this process of connecting Shopify store gets completed.