There are two ways to manage notifications. One is to manage the global app-wide settings for all groups and the other is to configure notifications just for a single group.
The app-wide settings will always override the group settings.
Manage App Wide Notifications
Tap the menu button in the top left corner
Tap "Settings"
Tap "Push notifications"
Manage Group Notifications
Aside from the app wide notifications, you can configure notifications specific to a group. This allows you to control which type. For example, if you're participating in a group with a lot of members, the check-in notifications could be bothersome. You can turn these notifications off for this group specifically, but keep check-in notifications on your other groups.
Navigate to the group whose notifications you want to manage
Tap the three dots in the right hand corner
Tap "Notifications settings"