Hi Martin, IIRC, I originally manually installed it (unzip or untar) to the EFI partition, used F12 or maybe it was the Arca Launcher, to boot to it and used itself to change the main boot manager to it. It ends up in \EFI\refind on the EFI volume.
Afterwards I found it not quite right and replaced it with the Deb from the site, which when I updated Mint, I had to downgrade to the version that Mint supported in its repository.
There's lots of information on installing it on their pages. Seems to me that installing it from Windows should also be fine, though any way you install you may have to manually edit refind.conf, especially if like me you have CSM enabled and want to boot legacy ArcaOS via AirBoot.