Adding tiers to memebrs created using the Admin API

We are planning on moving to Ghost from Patreon, and due to some policy issues (we make Canabis content), we can not use Stripe or even Paypal for that matter for our paymemt processing. So I have built a payment service that uses Authorize .net to process the payment. The users would be redirected to another page that I built in Node js to process the payment, and once done they would have their account created on GHost using the Admin API. So far, this is all working well, but I need to provide the users the ability to pay for different tiers. This shouldnt be an issue on my end with Authorize, since I can easily modify my terminal to intitiate the correct transaction wirh the correct amount based on the tier the user would like. However, how would I incorporate this data in to the members Object that is subsequently created? I can see that Ghost APi now allows us to create tiers using the /tier/ endpoint.
But is their a way I can specify what tier a member being created from the /memebers/ endpoint will be added to ?

Thank you so much for taking the time to read this, and I’ll appreciate any response I can get. Thanks.