How to upgrade it? Try to find a better way than building it from scratch. I'm assuming you're running some kind of BSD or linux. In which case your package manager will have a way to install a new kernel. In debian, typing
apt-get update; apt-get dist-upgrade
Would do it for you, assuming your /etc/apt/apt.conf file is configured to allow automagic kernel upgrading.
Tell us what operating system (including distro and version) you're running.