Install Raspberry Pi OS

First you need an operating system on the server

Just follow the official tutorial: https://www.raspberrypi.org/documentation/installation/installing-images/linux.md

Linux

It's simple on Linux. Here is my one-liner:

unzip -p 2022-01-28-raspios-bullseye-arm64.zip \
  | sudo dd of=/dev/sdX bs=4M conv=fsync status=progress

Or if you install something like LibreELEC

gzip -d -c LibreELEC-RPi4.arm-10.0.1.img.gz \
  | sudo dd of=/dev/sdX bs=4M conv=fsync status=progress

Or if you install something like Manjaro

xz -d -c Manjaro-ARM-xfce-rpi4-21.12.img.xz \
  | sudo dd of=/dev/sdX bs=4M conv=fsync status=progress

Source: https://raspberrypi.stackexchange.com/questions/32200/how-do-i-write-the-retropie-img-file-to-my-sd-card

Windows

It's simple on Windows.

Raspberry Pi Imager

Images downloaded by Raspberry Pi Imager are stored in C:\Users\YOUR_USER_NAME\AppData\Local\Raspberry Pi\Imager\cache. It stores only the last image by the name lastdownload.cache