How to install Linux Realtime?

Question

linux

Searched this question on Google. Found a couple of tips. At the very beginning, it was written that Linux RT is already included in Ubuntu (I have ElementaryOS Freya) and it is enough to execute:
apt-get install linux-rt
But the terminal only said that there is no such package. linux-rt tried to change to different:

linux-realtime
linux-image-rt
linux-image-realtime

Then I downloaded the package from the official repository. But I have no idea what to do with .patch.
It doesn't install like a normal application. I searched for "how to install patches for linux", but what I tried did not work:
patch -p1 < patch-4.4.2-rt7.patch
Although I did everything according to the instructions ...
Help the desperate. How can I install RT?

Answer 1

Before starting a discussion about how to build a kernel, tell me why do you need a low latency system?