Other than using DVD media to install Sabily in your system, you have an opportunity to use your USB Flash Drive as an installation tools. You need to make it bootable with an installation file on it same as DVD media concept.
I think this article is slightly popular in the net where I search on Google returned many result with a variety of explaination style. To make bootable USB Flash Drive in Ubuntu/Sabily is easy because the software is already installed and ready to use. Here I show how to make it with only five step to follow. My example is using Sabily full version ISO image installation file. After completed, this USB Flash Drive is ready to use as an installation tools and it can replace DVD media disc installation method. Please remember that your motherboard BIOS should have an opportunity to boot from USB drive, or you will waste your time to make bootable USB Flash Drive where you can't use it. To make bootable USB Flash Drive,
Insert your USB Flash Drive.
Go to System/Administration and click on USB Startup Disk Creator.
Click on Other... and locate Sabily ISO file.
Confirm Source disk image and USB disk to use, then click Make Startup Disk.
Now your USB Flash Drive is ready to use as an installation tools for Sabily.