We start with unequal heating at the surface . For example, an area 500 miles east of here may have warmer temperatures over the ocean. Because air will be rising, we therefore have an area of low pressure . Low pressure areas are always associated with air that is being uplifted . Notice the balance here - what goes up must come down.
All atmospheric activity takes place in the troposphere, remember.
Here in the Valdosta we may be having cooler temperatures. This causes high pressure. Therefore, high pressure areas are areas of descending air , air moving downward, because it is denser and heavier. This is what creates the area of high pressure. Fluids tend to move from areas of abundance to areas of deficits - think of siphoning gas from a car.