With this in the message area:
choose 'Go' to schedule an alarm. When 5:30 eventually comes around a window will pop up saying 'Time for dinner'. There's a close button to make it go away.
This alarm will happen in 10 minutes.
This happens every 30 minutes until you Cancel it.
If the alarm message _begins_ with 'SP_' then it is just spoken, not shown.
If _ends_ with '_SP' then it is both shown and spoken (without the SP, of course).
If the message is not spoken then the alarm sound is played at the time the alarm is raised. You can set the alarm sound by choosing Browse > Configure > Sounds (at the bottom) but can be overridden by suffixing the message with 'PL soundname' where the 'soundname' is the name that appears on the Sounds page.
If the alarm message ends with '_R' then the alarm sound will be repeated until you close the alarm window.
If there are pending alarms they will be listed in Browse > Configure > Alarms. You can cancel them there if you wish.
Finally, note that quitting Sue Center will cancel all pending alarms.