Add SaberSim to your phone as an app, open it, and allow notifications when it asks. After that, SaberSim alerts you when a player in any slate you have lineups saved for is ruled out or has their projection drop to zero, even if you're not using SaberSim at the time.
Open SaberSim in your phone's browser. We recommend Safari for iOS and Samsung Internet for Android.
Open the browser's settings and choose the option to add SaberSim to your phone. On Samsung Internet it's called Add Page To. Install it.
Find SaberSim in your apps and open it. The first time it loads, it asks whether it can send you notifications. Allow it.
If notifications don't arrive, check your phone's notification settings. On Android, the browser you used to install SaberSim has to be allowed to send notifications. On iOS, SaberSim shows up as its own app in the notification list, so check it there.
Mobile notifications are available on every plan. We also recommend turning on notifications in the DraftKings and FanDuel apps, since they send out-player news too.
Related: How do I Quick Swap?