Chipboard is more commonly called OSB, or oriented stranded board. Chunks of wood are laminated together and formed into sheets to make this building material. It is commonly used for roof sheathing, exterior wall sheathing, and for subflooring. Building codes dictate the correct thickness when using OSB as a subfloor material, so check with your local building inspector before you begin the installation.
Lay out sheets of OSB so they span at least two joist supports. Trim the OSB to fit if needed by marking the boards with a straight edge and a pencil; cut the sheets with a circular saw. Lay the sheets in place over the joists with the "This side down" label oriented correctly.