With OrbitKit, each of your accounts is a separate Venue. You can create as many Venues as you need, even if they are associated with the same Platform.
Just add a new Venue the same way you always do.
There are special instructions for platforms that require Airlock for authentication.
Note that if you want multiple Printful-connected stores, and they are all connected to the same Printful account, you only need to make sure that each Venue uses a different Secret Key (provided by Printful).