Creating Child Tokens

In the Authentication tutorial (Authentication | Vault - HashiCorp Learn), the a child token is created from a root token.

I am trying to create access for an app to access the vault. The user creates the vault using the web UI and has to give the app something, I am guessing a child token, how then, from the web UI do I create a child token?

If it does not make sense to create a child token, what is the recommended way to give access to this app to a specific user without giving the app the root token? The tutorial on the web UI (in the Getting Started tutorial Web UI | Vault - HashiCorp Learn) does not create a child token.