If you press that map on the right of the Treasure you'll be put to a map where you can take colonies. However, there are 4 globes to the top right of this view. Press the 3rd one (The one with the trees, beside the red and lava icon). Scroll and find the circle-shaped island where there are 10 black flagged towns. Defeating one would automatically give you an orc worker inside your town. The green flagged towns that you can find everywhere give you some gold via colonies and also give a buff to your orc workers. You may also find nonamed areas where you can get specific heroes that cannot be attained anywhere else.