To install an arm64 NixOS VM on the MacBook Air M1:
First install a Parallels VM for a supported Linux distro (Ubuntu, Debian, Fedora, Kali), then follow the guide for “installing NixOS from other distro”.
You can also run the x86 .iso of NixOS with QEMU/UTM as suggested in the previous post on the same topic but it will be slower than arm64.
Be aware that the NixOS image from the wiki on NixOS on ARM works well for Raspberry Pi and other boards but is not a good fit for VMs. You might want to build an installation image .iso for arm64 like the ones on the main site.