Setting up your Notification settings will decide how you are made aware of any changes to a client's situation - these can be through your browser, email or your Trail account. Any client notifications you have signed up for can be found in Trail next to your name and avatar.
The notification icon is a grey circle with a bell in the middle, which turns red when you have new notifications. Clicking this icon will open your most recent notifications. From here, you can click on any of the notifications to go to that client's Profile. Notifications in blue are unseen, and will turn white once they have been checked.