Your coach probably wants to track some of your data, in order to see your progress over time. Pretty much all data tracking is done using the Custom data feature.
With Custom Data, you can track absolutely anything with your coach. Here are few common examples:
Bodyweight
Waistline
Bodyfat percentage
Daily steps
Amount of hours that you sleep per night
Skinfolds
And pretty much anything else!
How to log your own data
Let's say you want to log your bodyweight (or ANY other data for today).
1. Go to your calendar
2. Click on the '+' for today
3. Select 'Custom data'
4. The Custom data panel will open on the right. You'll find the list of custom data that your coach enabled you to log in the dropdown list
5. Choose the data you want to log (in this case Weight) and enter your value for that day
6. Hit the 'Save' button at the top
After closing the Feedback window, you'll see the data logged in your calendar!