Temp Change during song

Hi everyone,
This may sound nooby but I can’t seem to find how to change the tempo during a song.
I can do time signature (Ctrl+T) and while in the same window if I change the tempo at the correct markers it changes the whole song. I can see the ramp and jump but I don’t know how to implement.
Is there something I’m missing ?
I am using Cubase 7 with latest 7.2 update (although missed the 7.1 update).

Should I also be installing 7.1 update as well or does 7.2 contain 7.1 ?
Will 7.1 update work if I install after 7.2 ?

The video on ‘Dynamic Tempo for Realism’ covers it.

http://www.groove3.com/str/Cubase-7-Tips-and-Tricks-Vol-1.html

So you´ve recorded audiotracks that you want to slow down or speed up at a certain point?

tempo track ?