By default OS X requires you to type in a password and login each time you restart your computer. If your computer is in a secure location, for example your office, you may want to set up OS X to log in automatically for you.
Here is how to do this.
Firstly will need to go to System Preferences from the Apple menu.
Then select ‘Users and Groups.’
Down the left there will be a little lock, you need to click this lock and then type in your password.
After you have unlocked the lock, you can click on ‘Login Options.’
Have a look where it says ‘Automatic login’ Off.
In the drop-down box change this from ‘Off’ to the user who you would like to be automatically logged in.
Now when your computer is restarted this user will be automatically logged in without having to type their password in.
Please note that if you have a laptop that you carry around with you and it is likely that it could fall into the wrong hands you probably don’t want to do this.
This removes all the security from your login.