@Wadehimeself 

I guess you are looking for the welcome flow? Usually that is the flow set up for new created accounts. 

How it usually goes is, if you properly integrated your account with Shopify you should have selected a list where new subscribers from shopify will go. So you should start a welcome flow started with that list that is your main list. Usually it is Newsletter list but it depends what list you chose. 

You can see this if you go back to integrations and check your Shopify integration to see what list you connected. Then use that list to start one of the pre-prepared welcome flows or create a new one yourself if you think you could.

See the img for the part of the Shopify integration that talks about the list connection

Hey @Wadehimeself,

Adding to @Bobi N.’s wonderful suggestion, in a similar vein, if you were trying to create a flow for when customers create an actually account in your store - think username and password, it would typically be accomplished through a metric-triggered flow initiated by a custom metric/event. 

We actually provided some examples of how to create something like a Created Account event highlighted in our Set up API-Based transactional events Developer Guide. 

I hope this helps!

David