Each of the categories (medication, activities, symptoms, sleep, weather, mealtimes) has its own page. You can disable all reminders and alarms for the item.
Use the priority button to assign the default priority level for reminders in this category. It can be changed when setting up the reminder.
To return to the previous screen, tap on the arrow in the top left corner.
Some of the categories have extra settings that you can enable or disable if you desire.