Remove any sources of food the ants find. Vacuum up all crumbs and remove and clean pet food dishes that may be attractive to ants. Store food in containers with tight fitting lids. If in doubt, keep the food in the refrigerator or freezer. Block or plug any entrances, if they can be located.
Caulk works well for cracks.
Put out ant traps. The worker ants enter the trap, feed on the poisoned material and carry it back to their nest. Once inside the nest, they feed bits of the poisoned material to the queen and immatures and the entire colony is controlled. Place the bait in a container with ant-sized holes in the lid. Place in a location away from children and pets, and dispose of the container after use.