Atticfoil is correct that there is a difference between a whole house fan and an attic fan, however a whole house fan doubles as an attic fan when it is running. Not sure where he thinks the air goes once it goes from the house to the attic, but common sense should tell anyone, it goes out the attic vents.
I'm going to guess this is a whole house fan, because of your description of the switches.
One of your switches should be a 3 position switch. On, Automatic and Off. The other switch is a timer, usually up to 12 hours and is set just like setting a kitchen timer by turning the knob clockwise. The 3 position switch has to be on automatic for the timer to work. On, on the 3 position switch should turn the fan on, until you turn it off.
Make sure you open some windows at least 2" or open a door or two to outside. This thing will draw huge amounts of air through the house. Enough to cause a slight breeze in front of open doors or windows. This is especially important if you have a wood stove or fireplace. If no doors or windows are open, it will draw air down the chimney and into the house making it smell like smoke and burnt wood. One more tip, this thing is great for if you burn something on the stove and cause smoke to fill the house. Just open a door and turn on the fan and the smoke will be gone in a couple minutes.
If this is actually an attic fan, most are turned on by a main switch, like an ordinary light switch and then they are thermostatically controlled with a thermostat that is built into the fan.