How can i use the 4 x 4 in my 2000 grand cherokee laredo (6 cyl) i dont have the owners manual and i dont know how to use my 4x4 on snow or something like that

Check here for the Jeep-WJ-Grand-Cherokee-Owners-Manual, keep in mind that the WJ series go to 1999 at 2004.

And here for knowed about 4x4 functions: Jeep.com 4x4

Hope helps (remember comment and rated this).

With the Jeep in park, move the left shifter to 4 wheel drive. Proceed to put right shifter into drive, proceed to drive. Only use 4wheel drive when neccessary...ie...snow, mud, use 4 wheel lo in steep incline or when really bogged down.

Hope this helps