Share Play:
What is it?
Basically its a neat feature that was added to the PS4 sometime ago.It lets your friends Play your games OR Play with you via the internet,Using Share Play your friend can either watch you play, play themselves, or play "local" multiplayer as if they are sitting beside you even if they don't own the game.If they do,Why are you looking here?
Ok but how do I use it?
I'm so glad you asked(I have no friends).
First of all, you both need to have a PSN account.
Create a Party on your PS4 and invite your friend to join.Then you load the game you want share play and press the share button (top left of controller) once it boots up,then choose "Share Play." Select the friend you want to play with and wait for them to accept your invitation. Once they accept, the PS4s will be linked and you can Share Play for 60 minutes.
NOTE:After 60 minutes you can just start another session,There isn't any limit.Take Advantage.
Once you are in the game, you can hit the share button again then select the option to let your friend take over control of your game. A Playstation Plus membership is required to hand off control, but it is not required if they just want to watch you and chat.The one who is initiating shareplay needs to be the one with the membership to pass the controller.
NOTE:Its actually pretty weird but sometimes you or your friend's network can cause problems.Not sure how,Me and my friend were unable to initiate shareplay but both our connections seemed to be ok(Although we had different speeds).I believe its something to along the lines of 'Two connections must be of similar speed' or something.
Enjoy!
P.S sorry about the Image Sizes,Was too lazy 
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