Accidentally deleted OS

[Boylsie]

So I accidentally deleted my OS when trying to reset my tablet back to fresh when trying to sell it. I'm currently stuck in a TWRP bootloop at the moment and don't know how to get out and reinstall stock android. I managed to get into download mode but my laptop doesn't recognise it as being connected in the LG Bridge app.
So I'm currently in TWRP menu and when I connect to the laptop I can access the memory. Are there any steps for getting android back on the tablet?

Thanks