Cubase 5 and alesis qx49 (Mapping)

Hey Guys.

Can anybody help me, I use ana alesis qx49 with cubase studio 5, how do I get all my sliders and Rotary knobs to work with my VST’s etc…
Example - I open my Vanguard VST, but cant use my rotary knobs to use the cut off or when i go to automate pitch shift or modulation wheel, even tho i’ve pressed the ‘write’ key nothing happens.
Is it something i have to do called 'control mapping ’ to assign all my qx49 sliders and knobs to cubase?
Please help.

I also have the QX49. Did you install the cubase script that’s on you Alesis disc?,
if you did the sliders will control the volume of each track and the knobs will control pan, if your vst instrument has midi learn, place your mouse over the control knob in your vst that you want to control ,right click and you will see learn pop up, just turn the knob on the QX 49 that you want to assign it to.