The manual install guide is good to go, but the stage4 install guide is still being worked on.
You need a program called a bootloader to start your kernel when you boot your computer. We'll use Grub2.
If using UEFI, you need to add
to make.conf. Now install:
> emerge grub
Now install Grub to the master boot record (MBR):
> grub-install /dev/sda
If using UEFI, this should be:
> grub-install --efi-directory=boot /dev/sda
If you get a "canonical path" error, you need to:
> mount -o remount,rw /boot
and grun grub2-install again.
If you are dual booting with Windows, you'll need to install os-prober:
> emerge os-prober
> grub-mkconfig -o /boot/grub/grub.cfg
At this point, you're done with the base Gentoo install. Now we're going to configure settings for audio.