I'd like to know about this too, but I think it's complex to work without the Galileo connected to the Internet...
Just a little advise: take into account that you have to use the so called "Intel® IoT Developer Kit version of the Yocto*-built Linux image" (IoT - Step 1: Make a bootable micro SD card | Intel® Developer Zone), not the one used for (Arduino) sketch persistency.
If you're trying to get files to the galileo without internet you might use filezilla. https://filezilla-project.org/
You do need to have the Galileo on your local network (internet not required, just a router).
the nice thing about this is it shows the directories on the galileo for those who aren't as familiar with the linux directories right off the bat. you can also move files around with it. Then uploading files or folders to the Galileo is as simple as right-click and upload!