After installing,

1. Setup essential services:

 # main tty
 ln -s /etc/openrc/init.d/agetty /etc/openrc/init.d/agetty.tty1
 /sbin/rc-update add agetty.tty1 default

 cp /etc/openrc/conf.d/agetty /etc/openrc/conf.d/agetty.tty1
 echo 'agetty_options="--noclear"' >> /etc/openrc/conf.d/agetty.tty1

 # additional ttys
 for i in {2..6}; do
   ln -s /etc/openrc/init.d/agetty /etc/openrc/init.d/agetty.tty${i}
   /sbin/rc-update add agetty.tty${i} default
 done

 # serial tty (for servers)
 ln -s /etc/openrc/init.d/agetty /etc/openrc/init.d/agetty.ttyS0
 /sbin/rc-update add agetty.ttyS0 default

 cp /etc/openrc/conf.d/agetty /etc/openrc/conf.d/agetty.ttyS0
 echo 'agetty_options="--noclear"' >> /etc/openrc/conf.d/agetty.ttyS0

2. Setup additional services

 Checkout out the openrc-services package and instructions provided
 there.

3. Add the following to boot parameters (via /etc/lilo.conf for lilo
 or /etc/default/grub for grub):

 init=/sbin/openrc-init

Regenerate boot configuration ('lilo -v' or 'grub-mkconfig -o /boot/grub/grub.cfg')

4. Reboot!

## Note

If migrating to OpenRC 0.39+ from previous versions, please check:
https://docs.slackware.com/talk:howtos:general_admin:openrc#migrating_to_openrc_039_from_previous_versions