I was following a tutorial ( How I Built The “Poor-Shamed” Computer… from someordinarygamers) and i think how to fix it but idk how to change and fix the issue from a bootable usb
Welcome to the forum 
Seems like a cool dude, don’t have time to watch 40 minutes tho, is there a step by step manual you can point to where you get stuck? Or better, ask the guy himself, in the first 30 seconds of the video he claims he is india’s favorite tech support.
well my main issue is i messed up not including one of the id’s and managed to add it from my bootable usb but i don’t know how to apply it because i assume the mkinit is the running system but idk how to do that on the main media from the bootable usb
not sure what do i need to look for/do since i am new to linux
Basically, what you need to do is just follow the Arch guide on how to set up GPU pass through.
He mentions it.
That’s all he used, that’s what he was paraphrasing from.
Then use the thusly configured System
to install another one via libvirt / kvm
(Windows in his example) - which is then set up to use the graphics card that you just passed through.
If you are new to linux, you might have bitten off a little more than you can chew right now 
… just my opinion …
You say you screwed something up - but no one knows at which step in the process you might have missed something important or where you failed - whether the initial pass through even worked or whether your hardware is actually capable of being used that way.
I can’t help you anyway - I don’t have hardware capable of passing through a GPU.
But if someone was to help you - much more specific data is needed for that to happen.