im new in parkour and i want to learn how to do it...any advices on where to start? right now im tryin to do the precision jumps and stuff in lower stages and i tried the kong vault but i failed. i gues i hav totally no experience in this thing. so where should i start and where should i go to train?

YouTube is definitely one of the best ways to learn the visual aspects of Parkour.  U$F has a series of good introductory videos.

First, you need to start conditioning your body.  Stretch and strengthen everyday, but don't touch weights.  Instead, do bodyweight-based exercises like various pushups, pullups, squats etc... to strengthen the major muscle groups, as well as the important stabilizers.  Also, practice moving around on all fours over all kinds of surfaces.  This will develop your proprioception and teach you "touch", or the sixth-sense of knowing exactly where each part of your body is at all times and how your weight is distributed.

To really begin understanding Parkour, get up, now, and go for a walk.  On this walk, try to see the world like a 5-year-old sees a jungle gym.  Walk on curbs, climb on walls, and try to step only on cracks in the sidewalk.  Actively look for obstacles in your path, and figure out how to get over them.  Make yourself do this everyday for 2 weeks, and I doubt you will want to stop.  You will start to feel more vibrant, the old obstacles will become easy, and your eyes will start to notice new obstacles that were hidden in the landscape.

Integrating (not shifting) into the Parkour lifestyle\mindset is important for gaining a personal understanding of the sport and ensuring longevity for your body.  Start exactly as you are and improve with daily baby-steps... your Parkour will develop itself with exactly the right pace and direction.  If you go one step further everyday, over time it adds up in huge, surprising ways.  Much like playing 5-year-olds celebrate the improvements over their baby-bodies, Parkour will help you will celebrate improvements over your pre-existing adult-body.

Hope this helps.