You can login as another user within the system, depending upon your permissions and the level at which you are within the system user hierarchy level.
The 'login as' button can be found against a users details, either in the users row when looking within the user list, or in the popup displayed when you click a users name from anywhere else in the system.
Clicking the 'login as' button will log you out from your account and then log you in as the selected user, bypassing their username and password request.
Once logged in, you will see from the top right of the screen, the name of the account you are in now shows the user you selected. Any additions, changes or deletions you now make will be recorded in the system as you, logged in as another user, ensuring the audit trail is not lost.