If you ever want to play metal you're gonna need to practice this a lot.

To do some palming muting is to rest the side of your hand just after the bridge ends. The more you approach your hand near the fretboard, the more muted (if that's a word) the sound is going to be.

Try this. Lay the side of your hand on the table, like a karate chop :) Then join your index finger and thumb as you would do to hold your pick. Now rotate your hand so that your index and thumb touches the table. This is the position you'll need to do palm muting. Sound silly but that's it. Now you have to practice picking while keeping the side of your hand on the strings.

Every guitar is different. I got two electric guitars and I need to position my hand diffrently on each to get the same sound.

Different pressure on the strings also modifies the sounds.

This is something you're going to have to experiement for yourself. You got to know your guitar a bit to be able to make a good palm muting. With time, it becomes second nature, you won't think about it.