The side panel on the main map screen by default displays your kingdom name, and below it - the amount of points you have gathered.

By hovering over one of your cities you can check how much points that particular city provides.

Tbe more points you have, the faster you king gains experience.

Points are awarded for buildings (this table details how many points for each), for each citizen (20+2*level for the elite, 15+1.5*level for laborers, 10+level for units), and for rebuilding towers (500 each, split between participants).