Before grabbing a pickaxe, get some information about the position of materials in the selected area. To do this, you need to scan through the ground with a geoscanner.
The main tool of material extraction is the mining module. The usage of mining modules is quite similar to weapons: they need to be equipped onto a robot, you need to load charges into them, and you need to lock a target for them to operate - in this case, a tile on the ground.
While in a terminal, equip your robot (try an industrial robot type) both with geoscanner and mining modules. Purchase the correct charges for them on the market, load the charge into the modules, then put extra spare charges into your cargo hold. Now, you're ready to extract materials on the field.
After you've deployed, you should begin by searching for materials. When you have the data of the material location, you need to prepare your mining equipment for drilling.
Lock a tile with your targeting computer, click on your miner module to activate it, and watch the materials flowing into your cargo hold. Each time a mining cycle begins, a certain amount of material will be added to your robot's cargo hold.
It's not the actual process of mining that makes industry difficult but the circumstances of finding, gathering, and protecting your materials. Since you're probably not the only one who uses an area for mining, be prepared for competitors, and ask for logistics or military assistance. Lone wolves won't get far in the cruel world of business!