OpenBSD provides a [[https://www.openbsd.org/faq/ports/ports.html|ports tree]] for installing software. You can find a copy of the ports from [[https://www.openbsd.org/ftp.html|the mirrors page]].
$ cd /tmp
$ ftp https://cdn.openbsd.org/pub/OpenBSD/$(uname -r)/{ports.tar.gz,SHA256.sig}
$ signify -Cp /etc/signify/openbsd-$(uname -r | cut -c 1,3)-base.pub -x SHA256.sig ports.tar.gz
If that returns OK, then the download was successful and valid. As root, run:
# cd /usr
# tar xzf /tmp/ports.tar.gz
To build a package from ports,
$ cd /usr/ports//
$ doas make install
(This last step is bad practice since building can be done without being root; only installation requires root privileges)