Download and install a specific kernel

[OBI_Ron]

Hello Everyone,

8.04LTS

How do I download and install a specific kernel?
2.6.24-16-rtai for example?

I tried sudo apt-get install linux-rt, and got the following:

Package linux-rt is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source
E: Package linux-rt has no installation candidate

Thanks in advance!