1. When user logged IN, add usermeta, say an additional option field which will save the time when user logged IN.
2. When user Logged Out, again create/add usermeta which will save the time when user logged out.
3. Take the difference i.e OUT time – IN time, and store it in another usermeta.
4. Create an admin page in backend, where you can list of all users with required data.
5. Table columns may include UserID, Username, In Time, Out Time and Difference (in hours).

Make sure your created page is visible to all logged in users.