If you’d like a particular application to open every time you log into (or start up) your Mac, now all you have to do is Control-click (or click-and-hold) on the application’s Dock icon and choose Open at Login from the pop-up menu.
Now restart your Mac and the application will launch automatically. If you want to hide the application after it automatically launches (so it stays hidden from view until you click on it in the Dock), here’s how: Go under the Apple menu (or to the Dock) to System Preferences. In the System Preferences pane, click on the Accounts icon, then in the Accounts pane, click on the Login Items tab. Now click on the Hide checkbox next to the application’s name. Close the dialog and your application’s set.