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 Dashboard screen, tap the "+" button at the bottom of the screen then select the "Add Activity" button at the bottom. Alternatively, open the Profile and tap "Open Activity View".
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.