Using a Carpenter Square, Find two pieces of scrap to support the square while you do layout on the corner.
Start by lining up the rise and the run on each side of the carpenter square. Trace those lines.
Line up with the previous step and then continue laying out the rise and the run.
At the top you will need to go down 1/4 inch to layout the header.
It is three quarter inch down south you can make a mark there as well.
Trace the end of that quarter inch.
You will need to do the same for the sill board at the bottom.
Layout that the sill board is 1/4 inch wide and three quarter inch deep.
Verify that you did it correctly. It should be 3-7/8" tall from top to bottom.
It will be 4" tall when we put the top tread on.
Cut everything out on the bandsaw.
Safety:
Cut slow and make sure to hold on to the piece so that your hand is never going directly at the blade.
Get the pieces for the header, bottom plate, and treads and use a miter gauge with the fence set to the correct width and cut them.
Nail together using 5/8" brad nails.