Help installing Nix

Hi all. I’m new to Linux. I’ve tried Linux Mint Cinnemon Edition and Manjaro KDE Plasma. I downloaded NixOS KDE Plasma after watching a video about this OS. I like how Nix is almost bullet proof when updating the softwares or the OS itself.

Now to my problem.

I built a new computer this week. Here are the basic spec:
Asus Prime B650-Plus motherboard
AMD Ryzen 7 7700 CPU
32Gb of DDR5
Sapphire Radeon RX 6800
Corsair mechanical keyboard
LG Hero 403 mouse
Corsair 2T SSD PCIe 5.0
Samsung 2T SSD PCIe 4.0

I heard in the past that I needed to install Windows (it’s currently on my Samsung SSD) before installing any Linux distro which I did. I’m trying to install Nix on the Corsair SSD. I used Balena Etcher to flash a Samsung T5 removable SSD and even the Corsair SSD but when I reboot the computer it loads Windows. When I go into the BIOS, I do not see the Samsung T5 or the Corsair SSD as a bootable option (only Windows boot manager is listed). What did I do wrong?

I managed to install NixOS. Updating my BIOS helped.