OpenBSD ports is a collection of third party software that are ready to install. These packages do not undergo the same security audit that the OpenBSD base system goes through.

Getting the ports tree:

[user@host ~]$ su -
[user@host ~]# cd /usr
[uesr@host usr]# ftp ftp://ftp.openbsd.org/pub/OpenBSD/`uname -r`/ports.tar.gz
[user@host usr]# tar xzvf ports.tar.gz
[user@host usr]# rm ports.tar.gz

Search the ports tree:

[user@host usr]# cd ports
[user@host ports]# make search key=keyword

Install a port:

[user@host usr]# cd appDir
[user@host appDir]# make install

References:
OpenBSD FAQ