Usually the Gentoo distribution is being upgraded by two simple emerge commands. Emerge is part of Portage which is the packet system of Gentoo.
The commands to upgrade your Gentoo system are:
user@GentooBox ~# emerge –sync
This will sync your local machine with the gentoo server that you have set in /etc/make.conf
user@GentooBox ~# emerge -uNDav world
This will print a list of all the available new packages for you as well as the upgrades for the existing ones. It will ask you to accept and continue.
The above commands will download and install all the software except the kernel which will be just downloaded and located at /usr/src/linux-2….
Once the kernel is downloaded you can proceed compiling it manually or use genkernel which can compile it easily for you. To install genkernel you can use:
user@GentooBox ~# emerge -a genkernel
More information about genkernel: Gentoo Linux Genkernel Guide