This quick article will explain how to install pkgsrc packages on an OpenBSD installation. This is something regulary asked on #openbsd freenode irc channel. I am not convinced by the relevant use of pkgsrc under OpenBSD but why not :)
I will cover an unprivileged installation that doesn't require root. I will use packages from 2020Q4 release, I may not update regularly this text so you will have to adapt to your current year.
$ cd ~/
$ ftp https://cdn.NetBSD.org/pub/pkgsrc/pkgsrc-2020Q4/pkgsrc.tar.gz
$ tar -xzf pkgsrc.tar.gz
$ cd pkgsrc/bootstrap
$ ./bootstrap --unprivileged
From now you must add the path ~/pkg/bin to your $PATH environment variable. The pkgsrc tree is in ~/pkgsrc/ and all the relevant files for it to work are in ~/pkg/.
You can install programs by searching directories of software you want in ~/pkgsrc/ and run "bmake install", for example in ~/pkgsrc/chat/irssi/ to install irssi irc client.
I'm not sure X11 software compiles well, I got issues compiling dbus as a dependency of x11/xterm and I got compilation errors, maybe clashing with Xenocara from base system... I don't really want to investigate more about this though.