Connected App Initial Access Token

In the Connected App there is an Initial Access Token and a Generate button for it.

The description for the field is as such :

Generate an initial access token for an org’s parent OAuth 2.0 client app. 
Salesforce requires this token to authenticate the client app’s request 
at the dynamic client registration endpoint.

In the online documenation this is written about that token :

After generating the initial access token, register it 
with your external API gateway.

How\where do I "register" that access token ?

Here is the full documenation I am referencing :

Generate an Initial Access Token (https://help.salesforce.com/articleView?id=remoteaccess_oidc_initial_access_token.htm&type=5)