After you download the GNS3, all you need to do is double-click on the GNS3-2.1.5-all-in-one file to begin installing it on your computer. Unlike Cisco Packet Tracer, GNS3 installation is a bit complex because several components are part of the installation process, and the majority of them are mandatory for GNS3 to run smoothly. Because of that, I recommend you follow the installation instructions carefully: https://www.technig.com/install-gns3-network-simulator/.
When you are done with the GNS3 installation on your computer, then it is at your disposal. Note that GNS3 user interface (as shown in Figure G.3) is completely different from its counterpart Cisco Packet Tracer. Another thing to consider is that you need to have Cisco IOS images, so you can work with switches and routers on GNS3.
