Patron is all about production, production chains, resources, manpower etc. It's no wonder then that an essential part of that is gathering resources. You have to start somewhere and in the beginning of a game, you don't have a quaint setup of foresters and sawmills. You have yet to reach that. What you do have are map resources, or resources that are available for gathering right in the game world. These are your very basic Lumber (cutting down trees), Stone (gathering lumps of stone) and Iron (iron deposits).
Depending on the map, you'll have more or less of these available from the start. It is advisable to start the game on one of the easier maps where these wild resources are more abundant. Keep in mind that these resource clusters, especially stone and iron, are just to get you started. You should never rely on them.
OK. That's the first step. What do I replace these with to make reliable sources? To organize a healthy supply of Lumber, you'll need to build Forester huts. Foresters plant new trees and cut down and process grown ones. They need quite a bit of space though, so don't place other buildings in their production radius.
The Quarry is your key building when it comes to creating a good supply of Stone. Don't forget to turn on the Ore richness overlay/grid to get the best efficiency.
The Iron mine will get you a nice supply of Iron.
Unlike gathering resources in the wild, these buildings naturally require workers to be assigned, hence why constructing them in the very beginning is not a good idea. In later stages, for example, after one or two winters, you should be looking in that direction.