Cot bumper

Debbie • 1st time mammy
This may sound like a really stupid question but I'm a 1st timer.....
Where do I put a cot bumper?
I've been given a set as a gift and its got a cot sheet, blanket and 1 bumper. Do i put it around the head part of the cot or the side? If the side.....which one and shouldn't the come in 2's?!