Hi there, and welcome to the Modplug Central forums.
Do you actually know how to do this? Have you been able to do it in other hosts, or are you completely new to all this?
The latter seems to be the case to me.
To control a parameter from a VSTi, a few things needs to be done. The host needs to know which parameter is controlled using which midi CC, and your midi controller's knobs need to be set to control a certain midi CC as well. By default neither are set, with the exception of the pitch and mod wheel, which use predetermined midi CC's.
Your first task would be to read the manual on how to assign a midi CC to one of your sliders or knobs or even buttons.
When I bought my SAMSON Graphite M013, to control parameters in my VSTi's, I ran into the same problem. Nothing happened. I found out that I needed to download a program to interface with it and program it that way (or use its buttons, but up to today, I still haven't figured out how that works)