there are several different ways to psi feed so feel free to try them to find one which is most comfortable for you.
Also I am not a Vampire so things may work differently for you but hopefully this will make sense to you and give you a starting point.
Fire and the wind are, I think, good sources to start with as they have a tangible physical effect to focus on.
If you feel the heat from a fire or the wind buffeting against your body you can concentrate on that immediate effect, then from a point in the middle of your chest visualise yourself extending a thread of light to touch the effect of your chosen source.Visualise the thread as something fluid or gaseous like a whirlpool or an electrical spark,then as the source energy is drawn into your thread change it to the colour of your power centre.
Your power colour will most likely be the first one that comes to mind or at least one you find really comforting, it may even be your favourite colour.
If you really can't decide try white as it is easy to visualise and contains all the other colours.
Now allow the heat or air pressure to enter at the point where the thread touches your chest wall and steadily draw the power into your energy center.
Take it steadily at first and don't let the effect overwhelm you.
If you start to feel dizzy or sick stop and pass back some of the energy then close the connection by visualising the thread seperating and withdrawing back into your power center.
I can't comment on how you will actually feel afterwards but you are likely to feel slightly euphoric and probably more full than you did.
Zygo