When an employee needs your OK before it acts, you can answer it as a card where it came up, in your Inbox, or from your phone.
In a chat
A card appears in the conversation describing what the employee wants to do. Choose Approve once to allow just this action, Approve always to allow this kind of action going forward, or Deny.
In your Inbox
Open your Inbox. Anything waiting on you shows under Needs your approval, with Approve and Deny buttons.
On your iPhone's lock screen
If the request arrives as a notification, you can decide without opening the app: Allow once or Allow always (you'll be asked to unlock your phone first), or No.
The first answer wins
A request you can act on from more than one place — your computer, your phone, your Inbox — closes everywhere the moment anyone answers it.