On the Website
If you open the Dashboard on the challenge website, you'll see a snapshot of your daily history in the left-hand column. You can click on this to view your full daily history.
Alternatively, go to https://<your challenge address>.bigteamchallenge.com/activity
The Daily Activity page allows you to view activity for each day of the challenge and also add new activity for a previous day.
On the App
Open the Home/Dashboard screen and select the "Add Activity" button at the bottom.
Now, select a day and you'll see all of the individual activity entries. You can select "Add Activity" to add a new activity for that day.