When you see 6b8 it means you will bend 6 up to 8 which is a whole step bend.

The same with 3b6, you will just bend it up 1 1/2 steps.

You want the first note to reach the pitch of the second note through the bend.

The X means a muted string either with a palm mute for left hand mute.

In this case
2
2
2
0
X

the low E string is palm muted and the high E string is not played.