Improving pop with settlers?

Whenever I build a city with a lot of build and sea resources (for quickly building powerful units and airplanes later on, and a boost to research), and no food resources, I try to move in settlers to increase the population. However, when I move one in, I don't see the population increase. How many settlers are needed for a 1 pop increase?

only 1... but you need to press (Y) to make that happen... it could be possible you did not press any buttons or pressed (X) like you would do to fortify an army. Look at the units available in that specific city maybe there are a bunch of idle settlers.