Cant use both my hard drives on my new setup

I recently switched from a windows setup to arch linux as the title suggests, I have backed up most of my important things on an external hard drive of 1TB, now my main issue is that i dont understand how handling more than one hardrive in linux works, I had no problem partitioning and setting up my SSD to run my OS on, I have 3 partitions on my SSD nvme0n1p1 which is my EFI partition, nvme0n1p2 which is my SWAP and nvme0n1p3 which is my linux-filesystem which is ~250gb, now i also have a 1TB HDD which i didnt setup in the initial installing process but i would like to utilize to store things like large files, VMs, games, tools(i want to install the blackarch repo there) but i am facing difficulties utilizing it, for starters to give some backround im running normal arch with just a WM (xmonad, specifically distrotube’s “dtos”), ive tried alot of things and have asked for help from many people to basically no avail, the closest i got to functionality was making a ext4 file system with fdisk and mounting it on a directory i called /HDD and putting a VM on there, but it got really annoying because to access anything on that drive you needed root privileges meaning i had to run virtualbox with sudo, additionally i couldnt get pacman to install software there instead of my SSD, i want to be able to have control of what goes where in my system, meaning that at any given time I’d like to be able to store stuff on my SSD or my HDD and have good control over both of them without it being a hassle. I tried LVM as someone suggested in the arch linux discord following a video by Chris Titus Tech but i got stuck due to the fact there is no existing volume group nor will it let me create one, also while looking through different ways to solve the issue we went over the scenario of backing everything up and re partitioning my drives to make a volume group when we realized that i also cant use my external drive since i also cant figure out how to get that working on my system without deleting all the files inside of it since it has all my important backups from windows. I dont know what to do but to summarize i want to have control over my 2 hard drives and be able to easily switch between saving data and programs on one drive or the other as well as getting my external hard drive to function without loosing my saved data. I know this is alot but I have been searching for hours to no avail.