You install it, then clone your GRUB (or LILO) entry so you boot passing init=/sbin/runit-init to the kernel and when you boot it, it should start on a rather normal-looking runlevel 3.
To reboot or halt, use reboot-runit and halt-runit, please!
Keep in mind that this is just a beginning, since all your services (except your ttys :-) are still running without supervision!
Should not destroy anything, but use at your own risk.
You will have to work further if you want to do more.
Included is /etc/runit/services/test a trivial template service.
Sorry about the spammy hosting, but I will get a decent server space for these files somewhere eventually. These rpms are just a teaser, anyway :-)