Panelolu2 on Ramps 1.4 - I2C missing ? (no replies)

Hello,

I ordered a Panelolu 2 to plug on the RAMPS 1.4 of my Mendelmax but it's not working.
I followed the install instructions from Think3dPrint3d but the only result is that I cannot use a computer-based driver for the printer. The screen is on when I plug the board to my computer, so I assume it is not broken ;)
Hence, I came back to my previous configuration of Marlin.

I noticed that the adapter for RAMPS has more connectors than I have pins on my board. I mean that my board has not any I2C pin. I guess this is why it's not working.
But what should I do to get such a I2C connector ? is there an add-on or am I supposed to solder new pins myself (since I'm a noob with electronics, I would avoid this ;) ) ?

Thanks in advance for you answers...