Mix a solution of two parts white vinegar and one part water in a spray bottle.
Watch the ants you see in your home. Find their nest by looking at where they are coming from and where they are taking food back to.
Spray the vinegar solution all around the area where the nest is located. The ants will not come out because of the vinegar smell. While the solution will not instantly kill the ants, it will keep them from leaving the nest, where they will eventually starve to death.
Spray the vinegar around any other possible entry points in your home, such as door frames and window sills, to deter any new ants from entering your home.