You're able to see your notifications by viewing the bell on the upper left hand side of your boards. Here is where you'll see that other team members have mentioned you in comments, pulses, etc.
When you receive a notification, you will see a number aside the bell indicating that you have a notification waiting for you to view. Click the notification bell and it will take you right there to the pulse :)
In order to send a notification, click on the @ sign and then the person's name as seen below