After installing this mod, if you start or load a game, there should be a tab on the bottom bar that says "Reminder" and/or has an alarm bell icon.

As of this posting, Reminders does NOT have any mod settings. If Reminders isn't working, there is likely another mod interfering, such as "UI Not Included". If this is the case, go to Menu - Options - Mod Options - <UI Mod>, and change the settings to move the Reminder mod to the bottom bar, and make the Reminder mod visible instead of hidden.

If that doesn't work, you may have a mod conflict, or a corrupted install. Consider visiting the Rimworld Discord at https://discord.gg/rimworld, visiting the Troubleshooting room, and reading the pins. This will tell you how to verify your files, take a hugslog, and other basic troubleshooting steps.

Once your issue is solved, don't forget to thank everyone involved and share your solution here in case someone else runs into the same problem.