If you are using SX first select master on the transport bar (this tells cubase to follow the master tempo set in the tempo track and ignore te rehersal tempo set on the transport bar) now go into the project drop down menu on te main arrange page and select tempo track. You will be presented with a graph and using the pencil tool you can now change the tempo by altering the blue line running across the center of the graph. To change te time signature click in the small space between the ruler and the graph at the point in the track you wish to alter. This will create a time signature symbol the same as the current time signature but this can be modified by changing the value in the signature drop down box in the center just above the ruler.
Hope this helps.
Keith
