Market Research Based On Geographical Zone

I would like to find all the companies who may use products similar to the ones i sell within a specific area. I have used google maps to draw the area and have imported the file as a KML. Im under the impression i need to use QGIS for the next part of it and i really dont have the skills required for that.

I would like to know all of the companies/individuals within the area that are in the steel industry. That way i can target my in person sales to the right areas. I will be after only company name and address.