How to layout and build a set of steps?

Figure out the rise and run. Like if you have to go up an elevation of three feet, you can use 3 one foot steps or four nine inch steps. Lumberyards and home improvement stores sell precut wooden stair stringers, you just have to attach them to a sturdy foundation and nail on your choice of treads.

Many ways to do this, here is one:

How to Build Stairs - Building Steps with Wood in 3 Steps - Popular Mechanics

As a rule of thumb when laying out your risers and treads:

Riser = 7" maximum
Tread 11" minimum