Open Facebook and go to your profile
Tap or click Friends
Select the pencil icon or More options
Choose Edit privacy
Set Who can see your friends list to Only me
Save the changes
On mobile, open the Facebook app
Tap the menu and go to Settings & privacy
Tap Settings
Go to Audience and visibility
Tap How people find and contact you
Tap Who can see your friends list
Select Only me
Confirm the change
Check your profile privacy settings to make sure the friends list is hidden