After to download OpenStage iso, you will need a program to burn image into dvd or usb stick. If you are going to burn iso on dvd you can use any program but if you want to burn it into usb stick you will need a specific program. Etcher allows you to burn iso into usb stick over Windows, Linux and MacOS. Probably there are more apps that will burn iso to usb correctly ( so you can test them ). For linux users also can be done with "dd" command.
Etcher app can be download form here.
Installing the iso
When you finish to burn image you will need to reboot your computer and select DVD/USB in your boot menu or set DVD/USB in your BIOS like primary device to boot. After that you will enter into iso boot-menu that will allows you to start the live system
Once inside the system, you will see an install icon on desktop, click it to open and follow intructions for install OpenStage in your computer. When the proccess finish you will only need to reboot your computer ( remenber to change boot options in chase you changed them on bios ) and start using OpenStage.