Depending on your account type, you can add between 15 (Unlimited Sat 15) and 50 (Unlimited Sat 50) vessels to your hotlist.
Once a vessel has been added to the Hotlist, its artificial delay, which is used for security reasons, is lifted and the position is shown in real time.
Click on the star icon "Add to My Fleet" above the vessel photo.
The following window will appear.
Again NOTE: This feature is available for FleetMon Unlimited Sat 15/50 only.
Do not forget to save your settings by clicking "Add to My Fleet".