First thing to do is highlight the part of the image that you want to tilt, or the entire image with the rectangle selection tool. Then after it's highlighted, click the mouse pointer tool. Go to any corner of the image, and the mouse should turn into a curved shape. Then tilt the image which way you want to.
Start bu opening you image. Then go to the select tab and select the entire picture that is to be rotated with the "select all" option. Then go to the the edit tab and go to transform the rotate. Then rotate the image to create the tilt effect.