Default Real Problems with My LG Optimus G LS970

I know all of you people are so smart!!!! Someone please help me.I had to sell my iPhone to pay for a car window someone broke on me in San Francisco.And until I can get work to buy a new phone I'm stuck with LG Optimus G LS970 (the Made IN Korea). OK so all I can get the phone to do is two things(one)when I plug it in,all I see is the (secure booting error!),(Cause Boot Configuration Verify)and/or (two) Download Mode(DO NOT UNPLUG)the device until the process is complete.I need someone to literally walk me through the whole process please I'm not the sharpest tool in the shed but I have been progressively getting closer I think.also when I plug it in to the USB port on My Toshiba Satellite it says the Full Jelly Bean on Mako cannot be found do I need to buy jelly bean Platform 4.1.2 or can I get it online. I'm stressing without a moble phone Please GOD!!! someone help me.!