When you have joined a challenge you will find the Newsfeed screen by swiping up to expand the bottom drawer.
The Newsfeed will by default show the distances and activity of all people on that challenge who have made their profile and activity public.
You have the option to filter your Newsfeed to show less people. If you are in a Group(s) you can filter to see others in the particular group, and if you are in a team you can filter to see the activity by those in a team. The restricted privacy setting allows you not not be visible to everyone, but visible to people you are in a team or group with.
Newsfeed Interactions
If you want to support someone else in the Newsfeed, there are 3 reaction types: Congrats, Love & Support. These act like sending the person an emoji. You can also comment on peoples activity.
If you see inappropriate posts or comments you can report these by tapping on the 3 dots.