Portrait Orientation Lock

I have an iPod 4th Generation that is using the 5.1.1 iOS.

Somehow my viewing orientation got locked in portrait orientation. How do I unlock the portrait orientation?

I'm kind of new at this orientation stuff. I just know that when I want landscape view I just turn the iPod right or left & the screen adjusted before & now it isn't doing that.

Please help me I can't play some of my games because they need landscape view.

Thank you in advance.

Sincerely,

john_r_l