Remove all of the broken concrete with the hammer and chisel. Level the bottom of the hole and undercut the sides. The undercuts will aid in retaining the concrete patching material for the long run.
Vacuum the hole to remove all loose material. Wash the hole with the garden hose. The hole can remain moist, but remove all standing water.
Coat the interior surfaces of the concrete patch hole with the bonding agent. Follow the label instructions as to application rates and disposal of the excess material. Some bonding agents may come in a spray bottle, while others may have to be brushed on to the surfaces.
Mix the concrete patch material according to label directions. Various products exist on the market with different mixing processes.
Fill the hole with the concrete patch. Work the material into the corners of the hole with the end of the 2-by-4. Level the material in the hole by straddling the hole with the edge of the board. Drag the board across the hole, moving it side to side to level the material.
Smooth the concrete material with the hand trowel. Allow the material to cure without foot traffic for at least 24 hours or according to label instructions.