It should be pretty simple. Just put your palm down over the bridge of the guitar until the strings are half muted. They chunk the strings with the pick.
Keep practicing until you get it right.

You might have a problem with certain guitars tho. I've tried several that I can't use that are difficult to palm mute with. I've found the simpler the setup the better.

It sounds like you just have to either practice a whole lot more or try a different guitar.
If you're signed up as a highband user there's a ton of lessons on palm muting with sound files and tabs. Just use the search feature.