Packages run reliably only on the version of OpenBSD for which they’re compiled. If you’re using packages, then updating your third-party software is very easy. (If you build your own software from the ports collection, you can still update but it won’t be as easy.)
First, check the Upgrade Guide again. It describes any intrusive changes to major software. Take any actions it recommends before continuing.
Before upgrading your packages, check your
$PKG_PATH environment variable. It almost certainly references the package directory for your previous version of OpenBSD.
# echo $PKG_PATH ftp://ftp11.usa.openbsd.org/pub/OpenBSD/5.2/packages/i386/
Find the package repository for your ...