To install laminate flooring on stairs start by removing the overhang or the underside of the stairs with a jigsaw.
How to install wood laminate flooring on stairs.
Alternatively you could cover the overhang with plywood to make it level.
Cut the flooring boards to size using a circular saw.
Once this is done measure and cut out your pieces of laminate to make tread pieces riser pieces and stair nosing.
You need to take care of the treads risers and stair noses which can get a bit complicated at times.
You have to ensure that there are no gaps and spaces in the flooring and it is complete and perfect in every way.
Apply flooring glue of the back of the boards and place them on the steps.