tempo change on Nuendo 4

Respected Sir
Please guide me about the change procedure of the tempo & scale of any loop.
Please guide me also about the procedure that how can I change the scale or tempo of any particular track suppose I have open 8 track to create my own music & among the 8, I want to change the tempo or scale of any particular track among that 8, so what will be procedure?
I shall be thankful if you kindly guide me & oblige