How do you set Facebook so strangers can't send you a message?

[Seerah]

I have been bullied a lot of the times on Facebook. Strangers and those people who are not in the list of my friends keep sending me messages that are really annoying. Specially now that I am engaged I would really appreciate any kind of help in regard to blocking any kind of messages from those who are not in my friends list on Facebook.
Mind you facebook has changed. Most of the answers I got on Google for my question those were based on the old settings of Facebook. Now it has limited option.
Can anyone please help me.

If you could also advise how to block my pictures so that whoever is not on FB shouldnt see my profile picture at all...I have noticed some people have a profile picture up on their facebook but if you are not their friends you cannot see the picture at all..it is an empty friend unless you are his or her friend.

THANK YOU IN ADVANCE