Remove any loose pieces of concrete from the crack. You may need a hammer and chisel to completely clean out the crack.
Use a Shop-Vac to suck small pieces of concrete and dust from the crack.
Purchase a concrete patch kit at your local home improvement supply store. The kit contains epoxy and concrete patch materials. Add the epoxy to the inside edges of the crack.
Mix the concrete patch according to the directions on the package. Spread the patch evenly in the crack and allow it to cure.