1. Go to www.arario.jp
2. Click Crossfire.
3. Click the second button from the left.
4. Use logic filling in your id and pass, click the small button next to your id before pressing the big (and obviously confirm) button.
5. Download CF:JP.
6. Install like any other program (spam the "next" button), second from the right.
7. All the buttons are in the same spot as CF:USA, it's honestly not in the least bit difficult. There is one new button split in to for quickplay and a little square button for your missions.
8. If you want to make a room, just click okay and change the options once in the room, once again all the buttons are in the same spot as CF:USA. Zombie Mode is the bottom mode.
9. You can go to the second mode (S&D) and the top setting makes it bounty mode (which is basically like playing CounterStrike with crossfire player models/maps/guns.
10. You can replace most of the CF:JP files with the CF:USA ones.