1. To combine something with something else. The thing being added can be named between "add" and "to." Did I add too much salt to the recipe?
2. To increase something in some way. The power outage simply added to our woes.
add (something) to something
to increase the intensity or amount of something by giving more (of something) to it. You added too much sugar to my coffee.
add to
v.
To increase the amount or intensity of something: The increase in fuel prices will add to the cost of living in the city. After I broke my arm, I added to my misery by chipping a tooth.