I'm sorry I don't understand. Can you read guitar Tab?, if not you should learn. There are a few tabs on UG of this song
That just means a full bend. Just bend the string (on the 4th fret, on the g string) until it sounds similar to the way they play it.
That is called a bend mate. You have to hit that note,and then use your fretting finger to pull the string downward in the direction of the ground on your fretboard (like, between both frets)
That way you heighten the sound of the note. A full bend means that you have to bend it so far that at the highest part of the bend the note sounds like a 5 played on that string instead of a 4.

got it?
ok thanks the boy friend of my sister have tell it me ^^ but thanks that you have try it ^^