I will be assuming that you are using the Windows 7 ISO linked here. You can use another ISO, but integrating USB 3.0 and NVMe drivers are on you.
Step 1: Use Rufus to put the ISO on a USB flash drive.
Note: I recommend you use legacy mode or CSM in the BIOS for installing any OS, you'll have to write it as MBR in Rufus for this.
Note 2: If you already have a Windows 8/10 install and want to keep it, you'll likely need to use UEFI mode, which Rufus defaults to. (GPT is UEFI boot partition.) But you should check your BIOS to see what mode your system is booting in.
Note 3: If installing in UEFI, you will have to disable secure boot.
Step 2: Download the Windows 7 drivers for your chipset here. If you have a B550 or X570 chipset, grab the X470 chipset installer.
Step 3: Check other drivers for any other hardware your board has.
Note: Very important you at least get WiFi and/or Ethernet drivers.
Step 4: Download Wufuc, and put it and the drivers you downloaded in steps 2 and 3 in a folder on the flash drive.
Note: Wufuc is needed for modern processors, because of the artificial block Microsoft imposed that prevents modern processors from getting Windows updates.
Step 5: Install Windows 7.
Step 6: Install the drivers and software you've downloaded from steps 2, 3, and 4. The AMD chipset drivers could try installing USB 3.0 and/or 3.1 drivers, deselect those.
Note 1: If you only downloaded a small amount of drivers, get the rest of the drivers you need on the page linked on step 3.
There will eventually be a post-install guide, maybe.