My suggestions are in brackets. I know you were mainly interested in punctuation, but I made a few other changes in the interest of flow as well. Hope this helps!
May you correction me this article with punctuation
[Please correct this article for me, especially the punctuation]
[This] article is about using the left hand [when playing] the guitar.
- In the first playing you'll find your self stretch the fingers togather on the fret but the correct way is by stretch each finger independently with completly relax for fingers (no tension in muscles) this skill is very important and will improve with practice on the excercise.
[When you first start playing, you'll find yourself wanting to stretch your fingers to the fret together. However, the correct way is to stretch each finger independently. Make sure that your fingers are completely relaxed and that there is no tension in your muscles. This skill is very important and will improve with practice.]
- The Shifting ( change the position on the fretboard ) :
The Arm is responsible for shiting, and all the fingers don't involve in shifting, only arm.The shifting starts
by remove the pressure (without any relax becuse it will cause a squeak) from the strings by fingers
then move to a new position by the arm. REMEMBER, the fingers should be in readiness to the new position.
[The arm is responsible for shifting, and the fingers aren't involved at all, only the arm. To start shifting, remove the pressure on the strings, but without relaxing. Otherwise, this will cause squeaking. Then move your arm to the new position, and make sure that your fingers are in readiness for the new position.]