If you forgot to bring your phone or want to record activities that are not step-based (swimming, yoga, aerobic), you can manually input those exercise in Pacer app.
Here is a detailed instruction on how to manually input exercise:
Open Pacer, swipe up on home page
Select "Activity" under "Log My Health Data"
Select activity type or select "custom"
Input your activity data and tap "Save"
To view or delete manually added entries, go to "Me" page and find "Activity & Log History"