Hi there
Im new to Arduino, and i have brought the Arduino Starter kit from Earhshine Designed plus an ekstra DC Motor.
Do i got the components to run two DC Motors? If yes how?
Thanks ! 
How many TIP120 transistors do you have? Will need (at least) 1 per motor. 2 if you want to be able to have it change directions.
I only got one. Cant i just plug 2 Motors to one Transistor?
Maybe - read the spec sheet on the transistor, see what it is rated for, and compare to the current needed by the motors.
I'm running out the door now for an appointment, please don't take my lack of responses for the next several hours as intentionallu ignoring you :-).
The 2 DC Motors:
Rated voltage 3V DC
No load current 0.34A max.
No load speed 16,400rpm ± 15%
Rated load 8.0 g.cm
Rated load current 1.07A max.
Rated load speed 13,100rpm ± 12%
Length excluding shaft 25mm
Diameter 20mm
Width across flats 15.1mm
Shaft length 9.4mm
Shaft diameter 2mm
Weight 17g approx.
The Transistor:
TIP-120 NPN Darlington Transistor
60v
TO-220 package
In packs of 5 units
I suppose you could, the TIP-120 seems to have good enough ratings for it.
Pay attention to the pinout, make sure you have a resistor between arduino pin and the base pin, a minimum of 220 ohm should be safe. Try that, measure the voltage across and calculate the current out of the arduino (V across the R)/R = current. Find an R that keeps it around 20mA, maybe 30 if your motors aren't going full speed. You can measure it directly if you have a multimeter with a mA setting; put your meter in series with the arduino output and the resister.
You might want to put a heatsink on the transistor (bolt a bit of metal to it to help dissipate heat).
Not sure what you'd do with 2 motors spinning in unison ...