Hydrogen: Authenticating on custom backend and using access token on shopify

Hi

I have set up a Hydrogen web application connected to my Shopify store. I want to authenticate the user on my custom backend using OTP login and then automatically log the user in on Shopify as well so that the user can start using the Hydrogen web application. For this once a user logs in I am using the customerAccessTokenCreate mutation to create an access token. But I am not able to figure out how to use this access token from the Hydrogen application?

When I setup the Hydrogen application it came with the boilerplate code to authenticate user using Shopify OAuth. Any help to modify this flow to use the access token I created above would be greatly appreciated.

Thanks