LBRP is really just clearing an area,when you get good at it usually 6months to 1 year it can also be used to banish things from your life as in cutting ties. There are plenty of articles analyzing the ritual in deep detail in the net do look around.
Middle pillar is a way to energizing your spiritual body, in other words strengthening your spiritual muscles. Do remember to do LBRP afterwards as it does draw astral bugs wanting some of the energy themselves, annoying things.
Unless you are born gifted, spiritual body needs to be built up from scratch to interact with any entities from the immaterium.
These are starter rituals be diligent to practice these daily.
Just an example if you are just starting out in terms of magical power you can't even lift 1kg of dumbbell yet.
Those ritual are like dumbbells that you keep on doing until you got more magical juice in you. Good news is you don't need to change the rituals it is automatic weight adjusted.
There are alternatives rituals of course. But LBRP and MP are easy to learn.
Quote: do I just ask for something?..with visualization? How do I make my request and to whom am I directing it at?
Nope you are not invoking or evoking with just MP, so you are not communicating with any being besides ultimate god I suppose.
Do visualize though,all ritual require visualizing to help develop the 3rd eye.