In order to refresh an access_token, you will need to grab the refresh_token value from the API response of your original request to retrieve a token:
You will then pass this refresh_token value as a query param in a subsequent request to this endpoint:
Refreshing an access token requires its own API request. Please keep in mind that each time you get an access_token or refresh a token, a new refresh_token value will be returned, so you will need to make sure you’re always using the latest value.
Let me know if this helps to clarify,