The armvm package will install a preconfigured ARM virtual machine named "f13-arm-beta1" with a 2GB image and a 128MB memory footprint. Since x86_64 processors don't provide hardware support for ARM processor virtualization, the ARM VM will run slowly compared to i386/x86_64 VMs, but the performance should be tolerable on most machines (Atom netbooks excepted). You can manage the VM with virsh or virt-manager. I've tested these packages on F13 and F14, but not on F15 Alpha yet. (By the way: the root password on the VM is "fedoraarm").
(Please don't forget that both the Fedora ARM beta release and the armvm package are very definitely at the pre-release/beta stage of maturity. In particular, updating the armvm package will REPLACE your arm VM with a new image - beware!).