This can be easily fixed with talcum powder applied on all the joints in the area of stair squeaks. Powder lubricates the edges and the noise should be cured.

Stairs usually squeak when there is a gap between the tread and the riser or the stringer. Amend such gaps with the help of wedges and carpenters glue and you will get rid of squeaks.

If there are a few spots where it squeaks it can be solved by calling a carpenter. However if it has become too old I guess its time to replace it.