The Ubuntu kernel repo

[personman]

How exactly do I add this repo?

sudo apt-add-repository ppa:kernel-ppa/ppa

Is what I get, but doesn't seem to work.

[claydoh]

What ppa is this, or rather, where did you find info for it?

There isn't an ubuntu-created ppa for mainline kernels, even though the url might seem like there is. You have to grab and install the needed packages manually.
https://wiki.ubuntu.com/Kernel/MainlineBuilds
Note that these are not for regular use, as they are fairly vanilla, and things such as Nvidia drivers usually won't work with them. There is more info on this in the linj above.

[acheron]

The kernel team have some conventional PPAs that can be added in such a fashion, but those should not be used by end users. If you come across those, it would not be advisable to use them unless you are directly and officially helping the kernel team test specific things.

As said, there is also the mainline 'kernel-ppa' which isn't an actual PPA in the sense it can be a added as one like the standard ones on launchpad. Sometimes in bug reports you will be asked to test latest kernel version which can be found in that repository, but again unless you urgently need a feature or fix that cannot be found in the stick kernels, you be advised to leave these alone as well.