Find Multiorders App in the Shopify App Store first and click on Add App:
You will be redirected to Multiorders with your email pre-filled. You just need to type in your password and Log In:
Once logged in, you will find your store already added under Connected Integrations on the left:
In the Status field inside the added Integration window, you should now see the status Import in progress. It might take up to 15-20 minutes to import your products depending on how many of them you have in your store.
When the status will turn Live that's it - integration has been connected successfully and products have finished importing.