Once you download and install Caffeine, launch the application and a small icon of an empty coffee cup appears in your menu bar. To activate Caffeine, simply click on the coffee cup and the icon changes to a steaming full cup of coffee. Simple and intuitive, what else can you ask for from a Mac app.
To launch the preferences menu for Caffeine, Command+Click the coffee cup icon and choose "Preferences". A window appears with directions for using Caffeine. Additionally, you are provided with options to automatically start Caffeine at login, to show the Preferences window when starting Caffeine, and to set the default duration for Caffeine to run.
The options for the default duration are Indefinitely, 5 minutes, 10 minutes, 15 minutes, 30 minutes, 1 hour, 2 hours, and 5 hours. In addition to adjusting your default duration from the preferences menu, you can Command+Click the Caffeine icon and select "Activate for" to set a different duration for the current session.
I know it may seem overly simple but a few weeks with this useful little utility and you will come to appreciate what a little Caffeine can do for your Mac.