heater blows out cold air

At the first cold spell I turned on the heater, but it blows out only cold air. The vehicle only has 57,000 miles ad all appears to be normal. there's just no heat. I added anti-freeze, attempted to change the fuse, but the fuse panel cover illustration doesn't appear to match the actual fuses, not to mention the fuses are next to impossible to put back in. I am attempting to "bleed" the system now by removing the radiator cap, running the vehicle with the heater on max. No change after 20 minutes or so. Help, thanks.