Find yourself a product called "Ant B Gone" It's a small container that has a clear, sticky liquid inside that you place where you see the ants travelling (they usually have certain routes from their nest). Do this for 2 days in a row. The first day you will see a ton of ants swarm this stuff! It's rather scary, there will be less the second day and by the third day you will see hardly any.
The stuff works well because the ants carry this goo back to the colony where it kills them off and eliminates your ant problem.
I had a big ant problem inmy townhouse a couple of years back and it worked perfectly! I highly recommend it!