Default [Q] restoring backup to bricked phone

so I totally bricked my stock rooted g2. I was messing with recovery and completely wiped everything including internal storage, now it wont boot but I can still get into twrp. I have my backup stored on my computer, but how do I get it back onto my internal storage so I can restore it with recovery? I tried adb sideload but nothing worked. is there a way to browse my computer through usb and copy it over? or I could temporarily install a rom just to get the backup back onto internal storage then restore it, but I cant figure that out either. I can get into download mode, but googling couldn't figure it out. I thought I could use fastboot command to wipe and install, but I cant figure how to get into fastboot mode. any ideas without having to flash stock and start over?