Folder with the question mark usually means "no valid device to boot from".
Try to boot to recovery (if any exists) by keeping pressing command + r when turning on the Mac. You should be able to reinstall it there.
If still fails you may try Mac OS X internet recovery (cmd+option+r keeps pressed while pressing power button)
If still fails, get someone with a working Mac with App store to get you a Mac OS X El Capitan Installer following the steps listed here:
Make sure the usb disk itself is a bootable instance (as in some cases it is blocked by hardware design).
When the bootable USB disk is plugged in, hold down the option when turning on to get a selectable boot device list and you should be able to see a disk to install to (if, not there is not any, it will be a hardware issue then -> go to Apple store or get someone else to fix).
After in recovery mode if seeing a disc to install to: feel free to erase the disk as Mac OS Extended (Journaled) (==HFS+) and install your instance with your Apple ID.