With the connectors pictures on the wiki I found the pin for the gnd , the positive on the trimpot it's ok 
You have been really  clear, it's  just that I made some electronics a long time ago, it's too far to remember all that I've learned, I more comfortable with computers(of course it's my job... )

I hope i'll be able to finish the How To by my own ....

You're right they are easier to hit than the test point on the pcb

Follow those steps exactly if you are still using Pololu Drivers (A4988's) ... But you can use the Trimpot itself as the Positive target and the GND pin as the negative one still - I find they are just easier to hit as they are much bigger than the tiny test point on the PCB itself...

To set the current that each stepper motor uses, you need to adjust the Stepper Drivers. On them, you will see small little dials - this is called a Trimpot.

You will need a Multimeter to adjust these.

Make sure the Solidoodle is connected to both USB and your external power supply..

First turn the trimpot all the way anti-clockwise.. 'turned down' if you think of it as a volume knob.
You then need to turn this clockwise, or 'up', until you get the correct reading on the multimeter. The correct value is vased on that table I posted - you will have to work out which 'sense resistor' you have, but if its a standard pololu, it'll be the 0.05 one..

You want the multimeter set to the lowest 'DC Voltage' setting it has. Then place the positive prove onto the trimpot itself (on the metal bit of the dial) and the other side on the top left most pin of the stepper board - it should be labelled "GND" meaning Ground.

Its a little 'fiddly' to begin with, but you'll work out the best way to hold everything..

Let me know if you need me to explain some more - I'm not sure if I'm being clear, But you can also try searching the forum for 'VREF'.. there may be some other guides/info as well. But feel free to ask if I'm still not making sense

I think I've understood quite all except that:

"Set your Stepper Driver VREF voltages"  ???

As I told you I have this card :
http://www.reprap-france.com/electroniq … 3%A9e.html

And I don't know what to do with this part of your how to !

You must change the setting in Configuration.h, recompile, reupload...

#define EXTRUDER_MAX_TEMP or something similar (can't check right now)... Its pretty obvious.