You may add a symptom from the care plan screen or directly from the check-in screen. Once a symptom is added, you can set reminders to be notified to record the intensity of the symptom throughout the day or week. You can also "link" this symptom to a specific condition or a specific care plan along with when it started. You can always manually record the intensity of a symptom by going into the Check-in screen, tapping Symptoms then setting an intensity.
If you don't wish to record the intensity and just want to record you felt a symptom, just click the checkbox on the top right of the symptom card. This box is also checked automatically when you slide the intensity slider. If you are recording a symptom at the end of the day based on when you felt symptoms throughout the day, you can also manually change the time you felt the symptom if needed. Otherwise, the symptom is marked as "Tracked" when you create the check-in.