The 3 different levels of VIP are Bronze, Silver and Gold. These can either be changed for a viewer manually by editing the viewer in the "user database" tab or automatically by that viewer donating a specified amount (If you have donations/tips setup). The default amount for this is $1 for bronze, $2 for silver and $10 for gold. These are the two ways to move a viewer into a VIP group.
You can also change the amount of points a VIP viewer gets by editing the points multiplier on the config tab.
Thanks,
Dante557
P.S. If you want to move users between VIP groups depending on the amount of points they earn in the month, feel free to request that in the feature request forum