Siftware sources

[William Frick]

I just 'installed' the Muktware Ubuntu manual for 12.04 from the software centre and received an email from Canonical advising me to add the following to my software sources
"deb https://**********************@private-ppa.launchpad.net/commercial-ppa-uploaders
/muktware-ubuntu-manual/ubuntu precise main "
-
In older ubuntu I knew where and how to do that but I can't find where to do that in 12.04.
The answer would be in the manual I presume but even that is somewhere less than obvious .... as in I can't find it ! 

After following last weeks "Rocket Stick" install question I can sympathize with the new user. It seems to me the nuts and bolts of ubuntu are becoming harder to find and hence adjust.

Sugestions anyone ?

Bill