"To set an alarm" means to program or adjust a device, typically a clock or a phone, in order to make it produce a sound or signal at a specific time to wake you up or remind you of something important.
Sentences with «to set an alarm»
So set your alarms for 2 p.m. to join the fun! (foodbabbles.com)
There will be plenty of changes, from working a different timetable to setting that alarm clock for the same time every day. (inspiringinterns.com)
Now set an alarm on your phone for every two to three hours after this time throughout the whole day. (juliedillonrd.com)