'Log Time As' enables Users to log Time Entries on behalf of other Users. This ability is permission-based—Users must be granted permission to access the Time Entries object via Salesforce setup, and Users must have permission to log time on behalf of others in Time Tracking Admin Settings.
To enable another User to log time on your behalf, click Manage Profile from the Time Tracking app > Scroll to 'Team' > Ensure 'Can Log Time As Me' is selected > Click Add Access > Search for the proper User > Click Grant Access.
View Users Who've Granted You Permission to Log Time As
To view Users who have granted you permission to log time on their behalf, click 'I Can Log Time As.'
How to Log Time as Another User
From the Time Tracking App, click the Down Arrow next to your username > Click the User for whom you'd like to log a Time Entry
On a Specific Date
Click the Plus Icon (+) on the date the Time Entry occurred > Fill out the required information > Save.
From the 'Add Time Entry' Button
Click the '+ Add Time Entry' button > Fill out the required information (including Date) > Save.