Setup for Restore. First of all, in order to be able to restore your system you need to configure a Time Capsule backup before you do anything else. I.e. your system will be restored into those ascertainments which where valid at the time of Time Capsule backup creation. If you do not do this, you will not be able to restore your system to a previous date so you need to take care of this thing first. If your computer is experiencing some serious errors that you can’t solve and you don’t have any valid Time Capsule backups, there are only two options left – to repair the hard disk or reinstall your OS.
Configure your backup. In order to set up a Time Capsule backup you need to connect an external hard drive to your Mac and make a copy of your hard disk in it. Needless to say, it has to be greater or at least equal in size with your internal hard drive. In case you are setting a backup for the first time, you will be asked if you want to configure the newly connected drive as the Time Capsule. If you want to protect your files from the third parties, you can use an option called “Encrypt backup Disk” and set a password to it.
Be patient. It will take some time till your files will be transferred to the external disk. You can command your system to make automatic backups and save specified files periodically. This option is available from Options menu.
Restore your system. In order to open OS X Recovery Tool press and hold down the command key + R when your system boots. When Recovery Tool is open, select the option “Restore From Time Machine Backup”. This will load files from the latest restore point. If on a given hard disk you have more than one backup, you will be asked to choose one of them. Select the one which is closest to the date when problems occurred on your system. This method can also be used to restore particular files that were lost (if you selected to save them in Time Capsule).
As mentioned before, if you do not have any previous Time Capsules to which you could restore your system and you don’t know how to deal with occurred problem, you can try to reinstall your system. From the same Recovery Tool menu, select “Reinstall Mac OS X”. To complete this action your computer needs to be connected to the Internet. It is also worth mentioning that after reinstalling you will lose all your files and programs, as well as settings.