USB connect method:
Just connect the usb to your PC.
Windows update will do the rest.

Bluetooth connect method:
Requires at least Bluetooth v2.1+EDR to pair one controller.
Check Dualshock 4 specs[www.playstation.com].
Recomend Bluetooth 4.0.

• PS4 Controller:
  Press and hold PS button ( The one on the middle ) and the share button for 3 seconds until the lightbar begins to flash.
  
• PC:
  The bluetooth will detect the PS4 controller as "Wireless Controller". Connect to it.
  ( If asked for a password, type in 0000 )

Windows 10 will automatically install drivers for you to use it, so you don't need any extra programs for drivers or mapping.

1. Go to Library.
2. Right click on "Assassin's Creed II" and select Properties.
3. In general Tab > Set "Steam Input Per-Game Setting" to "Forced off".

And on Steam Settings:
Controller -> General Controller Settings - Then select "PlayStation Configuration Support"

Edit this file ( Edit, DO NOT CREATE ):
"%AppData%\Ubisoft\Assassin's Creed 2\Assassin2.ini"

Remember :
%AppData% = C:\Users\<Your username>\AppData\Roaming
If anyone wonders.

Add this lines to the end of the file:


Note: Search for the Wireless Controller entry and overwrite it.
Remember to select Wireless Controller in the game Options.

Note 2: Run the game once for it to create the file, then edit it.

Save it, give a like to this Guide and start gaming.

P.S.: If your camera start spining out of control, quit the game, redo the code above, save the file, and change the Attribute to Read-Only. Now you can game correctly. ( This might be due a faulty System or Game Installation - My recomendation is to do a Fresh Windows Install whenever you can ). - Thanks to Goro Majima for pointing this out.