I am trying to log into my PC at work from my Mac. It requires Control + Alt + Delete key combination to login.
How do I do it from my Mac?
Depends on how you're controlling the remote PC. On most remote control software, you select "Ctrl-Alt-Del" from the menu to send the command to the remote PC.
The option key on the mac keyboard is also labeled alt and there is usually a delete key, too on larger / external keyboards.