Your text book(s) contain instructions on how to perform constructions such as bisecting angles, drawing perpendiculars etc.
However the exercises they give are normally fairly dry. These pages show you some constructions you can apply those skills to and are hopefully a little more engaging.
This construction inscribes a triangle, ie places a circle inside that touches all three sides once.
To carry out this construction you must first bisect the angles to find the incentre. Then draw a perpendicular from the incentre to any side and finally draw a circle, centred on the incentre that goes through the foot of the perpendicular.