If you already download Sabily ISO file, then you need to make a boot disk from it in able to install it. First you must install burning software like Nero or Devede if you using Ubuntu. If burning software is already install, then it is easy to you to make boot disk by double clicks your iso file or right clicks and choose to open with your burning software. For example in Ubuntu, double clicks and Write to Disc menu will appeared. Insert your blank DVD media, then select Write. Just wait until writing finished then your Sabily DVD is ready to boot for new installation on your system. Same procedure also apply to Windows user.
Example Write to Disc GUI