The commonest species that invades houses is the Black Garden Ant, which is actually very dark brown.
First find the nest entrances. These are indicated by small piles of earth pellets or by watching the ants moving back and forth from nest to food.
Pouring a kettle of boiling water over the nest site is a first-aid measure. This should be followed-up by puffing an insecticidal powder product into the hole. Select a powder product which lists ants on its label and read the instructions carefully before use.
An insecticidal lacquer can be applied around door thresholds or wall/floor junctions where ants run, or spray these areas with an insecticidal aerosol which is labelled for this purpose (ensuring you read the instructions carefully before use).
Alternatively you can contact a private pest control firm.