Assuming you have obtained legal images, here is how to integrate them into GNS3.
Importing Appliances: Use GNS3 "Appliance" files (.gns3a) found on the GNS3 Marketplace. These files act as templates, automatically configuring the correct RAM, CPU, and interface settings for your specific image.
Fire up GNS3, import your first image, and start dragging those icons onto the canvas. The only limit is your imagination (and your RAM).