How to restore a Mac to its factory default settings?

hello!
i want to restore the factory settings of my mac.
i reaed that i can to do it's.
i know that i need to confirmation to this computer after this.
i cancel in the sertificant of my computer, but wen i am installing the system i get exactly the settings that has were before it's.
what i can to do other to succsie to do this?
i go to osx utilities and i chuse in reinstall osx, and i not know to do.
i am happy to yours help/
thenk and have a good day.

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#1 clean install

Member of the AppleVis Editorial Team

Before reinstalling OS X, choose disk utility from the OS X utilities table. Navigate to your hard drive or volume your system is on, Macintosh HD if not changed. Select the erase tab, choose Mac OS extended journaled as the format, and click the erase button. If you want to set options for a secure erase, click security options and use the slider to determine the level of security for your erase. Keep in mind that this erases all your data, so you should make a backup of all important files. Once erased and reformatted, quit disk utility and choose reinstall OS X from the OS X utilities table.

#2 Thenk you for your comend.

I try to do this. Thenk for your help.