Luckily it's a very quick and easy process ;)
There are 3 main steps:
1) Export Customers from Shopify
Go to your Shopify Admin Dashboard -> Click Customers and click Export
Once you do, you'll get a lovely CSV file with customer information ready to be imported in MoonMail. 1 down, 2 to go.
2) Prepare a MoonMail List
Go to your MoonMail Account -> Lists and create your super amazing Shopify list.
Great. We're almost there. Just one small step to go and that is uploading your CSV file.
3) Upload the Customers
Now for the fun part. Getting those customers in the list and making use of the data :)
Once your list is created and ready, go to Manage Subscribers, Import Subscribers. Drag and drop your exported CSV file, associate the proper fields (name, surname, email and custom fields) and enjoy the show!
You are now ready to go and use the list to get more $$$.
Best of luck!