The Gentoo site provides a good documentation about installation.
The distribution files are found in /usr/portage/distfiles.
Compressed packages can be copied into this directory before attempting an emerge.
Check for the availability and versions/variants of component with
emerge search <component>
Download (fetch) the required files of component with
emerge -f <component>
Check for dependencies of component with
emerge -p <component>
Install component with
emerge <component>
env-update && source /etc/profile
Install masked component with
ACCEPT_KEYWORDS="~x86" emerge <component>
Find the most recent version of Gentoo ebuilds on the Gentoo portage site.
Download it to /usr/portage/<path-to-ebuild>/<ebuild-name>.
Check that the ebuild was placed properly and install it:
ACCEPT_KEYWORDS="~x86" emerge search <ebuild>
ACCEPT_KEYWORDS="~x86" emerge <ebuild>
If asked to do so, you might have to:
ebuild /usr/portage/<path-to-ebuild>/<ebuild-name> digest
After installing a deamon, it can be included in the system startup with
rc-update add <daemon> default