Introduction To Chrultrabook

Hi I have a Dell Chromebook 3100

I have tried reading the tutorial but I simply do not get it and I would like help, the HWID is FLEEX
and I am trying to install Arch Linux on this Chromebook by dual booting with chrome os and using a USB for arch Linux taking up the entire USB which is 256GB and if there is I would like to have a boot menu to choose between arch or chrome os and not lose any data with developer mode. Please could someone help me.

EDIT: I would like to use Submarine for the boot menu if possible

did you read the link?

Please note, Submarine can NOT boot ChromeOS in its current state.

that’s a hard no.

then i wont use Submarine what about the rest of it?

Start here: Legacy Boot Mode / Alternative Bootloader (AltFw) | MrChromebox.tech

Where do you get stuck?