Netatalk provides Macintosh file and print services. The OpenBSD generic kernel does not have support for netatalk, so you will need to build a custom kernel.
Go to the config directory for the architecture of CPU you have. On Intel architecture it will be /usr/src/sys/arch/i386/conf, on SPARC it will be /usr/src/sys/arch/sparc/conf, etc.
In there is a file 'GENERIC' which is the config file for the generic kernel. Make a copy of this file, with a suitable name for your computer. The generic config includes another file, '../../../conf/GENERIC', which will also be needed.
cd /usr/src/sys/arch/i386/conf cp GENERIC GATEWAY cp ../../../conf/GENERIC GENplusATALK
Edit the GATEWAY file to include GENplusATALK instead of ../../../conf/GENERIC. Edit the GENplusATALK file to uncomment the option for NETATALK.
Configure. build and install the new kernel:
config GATEWAY cd ../compile/GATEWAY make depend make mv /bsd /bsd.old mv bsd /
At this point the system will need to be rebooted to load the new kernel. The old kernel, now called bsd.old, is sitting in the root and can be used if the new one doesn't work.
Install netatalk from the ports.