This function is called impersonating in Zenu. There are 2 ways you can do this, which are covered below. You will need permission to Impersonate so check with your System Admin if you have issues completing this action.
One
If you are a My Day user just click on the drop-down near your name and select the person you want to impersonate.
Two
Click on your image top right and select to Impersonate
