How to install the stairs on wooden structures.

Drill a hole, 8 millimeters wide
Insert tags in drilled holes and to hit the step lightly from above.
Drill the hole in the wooden step φ 14 to a depth of 25 mm.
To press dowels into the wood structure and to drive in a screw.
To put glue on the wood structure and dowels.
To fill the step to dowels and the wood structure