Select System Preferences... from the Apple menu at the top left hand corner of the screen.
Click the Accounts icon from the System Preferences window.
Click to select the Login Items tab.
Click the lock at the bottom left hand corner of the window.
A popup will appear asking for an administrative login. Enter your username and password and click ok.
Notice the lock is now unlocked!
Click the + button to add a new login item.
A window will popup asking you to select the item to add. Select an item then click the Add button.
To hide an application when you log in, click its Hide checkbox.
Press Command+q on the keyboard to close System Preferences.