Lark reads and writes activity and health data to and from your phone’s default Health apps. For iPhones, this would be Apple Health and for Android users, this would be Google Fit. If third party apps or devices you have write this data and send it on to Apple Health or Google Fit, then Lark should be able to see it and track it! If they do not (like FitBit, for example), then this data would not be tracked by Lark.
However, you are always able to manually add activity by tapping on the plus symbol on the lower right side and by then tapping “Add data...”. You can then tap on the type of activity you would like to add, recording the type and duration.