Setting up network connection and upgrading the system would be my first post-installation activities.
If you want to start kde, you quite likely need to configure X first: In the command line type "su" (without quotes) to become the root user. Then run "dpkg-reconfigure -plow xserver-xfree86" command and answer all the questions. Then type "exit" to become a normal user again, and start kde with "startkde" command.
You might want to read Debian Reference, which is a post-installation guide that will help you to get started with your Debian system.
http://www.debian.org/doc/manuals/re...erence.en.html