This time I power-walk you through each command to install Gentoo (using a Hardened Stage 3 toolchain). I used this same set of commands, with a little modification of course, to install Gentoo onto my desktop. My hardware configuration is very unlikely the same as yours; adjust accordingly, otherwise these instructions should be all you need to tackle one of the hardest distro's to install (by reputation).
And before you tl;dr, realize that even though the process is long and gruesome, there's so much to learn by just even trying, so do not dispair. There's tons of resources out there! Good luck.
# mount /dev/sda3 /mnt/gentoo
# mkdir /mnt/gentoo/boot
# mount /dev/sda1 /mnt/gentoo/boot
Download and extract latest stage 3
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# cd /mnt/gentoo
# wget http://ftp.ucsb.edu/pub/mirrors/linux/gentoo/releases/amd64/current-stage3/hardened/stage3-amd64-hardened-20120621.tar.bz2
# tar xjpf stage3-*
Download and extract latest portage snapshot
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# cd /mnt/gentoo/usr
# wget http://ftp.ucsb.edu/pub/mirrors/linux/gentoo/releases/snapshots/current/portage-latest.tar.bz2
# tar xjf portage-latest.tar.bz2
Mount relevant directories and chroot into new environment
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# cd /
# mount -t proc proc /mnt/gentoo/proc
# mount --rbind /dev /mnt/gentoo/dev
# cp -L /etc/resolv.conf /mnt/gentoo/etc
# chroot /mnt/gentoo /bin/bash
# env-update && source /etc/profile
Continue by customizing your install with a browser, file manager, window manager, or be lazy and just get a whole desktop environment. Have fun making any necessary tweaks to file's we've already used, like make.conf USE flags, kernel configuration, bootloader.. but be happy, if you've got this far, you've got a working system.