I have thw wiring, but i dont know the code 
Can somebody write it and expain it to me please?
Pot: 1k ohm
Led Blink: 5ms to 500ms
thanks inn advance
Well, I'm not going to actually write code, but...
In the original blink sketch, the led is turned on, then delay() is called. That basically pauses the program for the number of milliseconds specified. Then it is turned off and delayed, etc.
But now you need to use a variable instead of a number. You must assign the variable the value of the pot every time loop() is run.
But this gives you a 0-1023 ms range.
So, you use the map() function. As it's parameters, use analogread as the variable, 0-1023 as the old range, then whatever range you want as the final one. Assign this to the variable instead.
If any of this doesn't make sense, a quick search on the arduino website should clear things up.
thank you much, i wrote it, and it works!