It's actually not too complicated, ME is the one variable people care about the most (This makes the item waste less materials when you make it, effectively making the item cheaper to produce). PE only lowers the time required to make the item, and most items can be built relatively quickly, so it's often not researched at all except for certain long-time manufacturing jobs.

Basically you spend time increasing the ME and PE of the item via Research to make it more efficient to produce, then you make copies (that can only be used X numbers of times) and sell them for profit.

The problem is exactly what Brendan highlighted, it's very difficult to get into for new players just because you will usually have at LEAST a 1 month wait to get your turn at a research station anywhere in highsec. If you want to get into research and can't afford your own personal POS, I recommend getting a covops frigate so you can run down your valuable BPOs to abandoned areas of lowsec where the queues are much more manageable