Sleekplan is integrated with Shopify. Just install the Shopify app and follow the instructions to get started.
Add the Sleekplan App
Go to https://apps.shopify.com
Find the Sleekplan App
Click on 'Add app'
You'll get redirected to Sleekplan
Enter your login & password
If you have multiple Workspaces: Select the Product/Workspace that you want to link with your Shopify account
The Sleekplan widget should now appear on Shopify