HT1338: OS X: Updating OS X and Mac App Store appsLearn about OS X: Updating OS X and Mac App Store apps
Currently Being ModeratedMay 3, 2012 3:10 PM (in response to makbrahman)
Your account password for logging in can be set or changed in the "Users & Groups" system preferences. Select your account in there and then click the "Change Password" button.
Currently Being ModeratedMay 4, 2012 3:59 AM (in response to makbrahman)
If your account is currently being logged in automatically, you need to stop that. Go to System Preferences -> Users & Groups, click the Login Options button, then click the lock in the bottom left corner of the window, if it's locked, entering your password when asked. Finally, select Off from the Automatic Login pop-up.
Note that your account already has a password, so if you don't know what that password is, you may have some difficulty. You can't change it without knowing the current password. There are ways to reset it, if you get into that situation.