Students: Instant Messaging in Office 365
KB0010586
You can start or accept an IM session with someone directly from Outlook Web App.
You can sign in to IM by selecting your name at the top of the Outlook Web App window, then selecting Sign in to IM.
Once you're signed in to IM, select your name again, then select your status.
To start an IM session
Find the person you want to send an instant message to. You can look them up in People, or find a message from them and select their name to see their contact card. Select IM to open an IM session with that person.
To accept an IM request
A contact might start an IM session with you. The request will appear at the top of the Outlook Web App page. You can either Accept or Ignore the request.
To accept the request and respond, select Accept.
Type your response and press Enter.