Hiya,
I'd suggest reading/working through this blog post: https://fusionauth.io/blog/2020/03/10/securely-implement-oauth-in-react
You have to do a couple of things (provide the right scope, pass the correct JWT back to the correct endpoint), and it might be fastest for you to read through that and post any questions you have. (If you aren't comfortable in javascript, please let me know which language you are comfortable in and I'll see if I can dig up an example.)