This is how to secure a Facebook Account.

STEP 1

Adding "Two-Factor Authentication", Login to your Facebook account and click your profile
By then click the "Settings & Privacy > Settings".

STEP 2

Click "Account Center"
And go to "Password and Security"

STEP 3

Add "Two-Factor Authentication" under Login & Recovery Section.
Type your Facebook Password and add Authentication
(Note: We Recommend using both Authenticator & SMS, But SMS should be fine *Buyer's Number*)

STEP 4

Under "Account Center" click on "Personal Details" then "Contact Info"
Last part "Add new Contact" and Change Facebook Password
(Note: In this part Seller's Contact should not be on the account anymore, If there is DM the Middleman)

STEP 5

For Additional Security, Under "Account Center" click on
( Password & Security > Where you're logged in )
And remove Unrecognized Devices