A couple of weeks ago we enabled Chat on our Community. For you to be able to chat with other Community users through our chat app, you need to add them to your network. To add friends, just hover over the user name, click "add as a friend" which will then open a little pop-up window where you can add a few words. Doing so you have send a friend request that would need to be approved by your friends.
On a regular base I'd like to suggest you to check if you got some friend requests pending.To do so, next to your avatar picture click your name to reach your profile. In your profile page, click the tab-folder "Friends" and then choose the "Requests to Review" option where you should see all pending requests for you to accept or reject
Depending on your email and notification settings (follow this link to check these) you may or may not receive an email to let you know you have pending requests.