Here are the basics instructions to setup Facebook 2-Factor. This will send you a text on your phone and tie into the Facebook app on your phone to give you a code when you try to login. You can save/exempt your computer from being prompted going forward but this will give you a warning when someone tries to access your account.
First step is to go into settings using the dropdown on the top right.
On the next page, click the Security option in the top left corner
Next click on Login Approvals
Fill in the information and turn this feature on. Going forward, you phone should generate a code if you try to login on a new computer.