The forms in intellect are some kind of blueprint or model on which the physical world is based, and something needs to come along and shape the matter in accordance with that blueprint. What does that is soul.

Plotinus is a neo-Platonist, so he would encourage us to go back to Plato.

Assuming there is an intellect, we're clearly not this universal intellect or we would know it. So that's one function of soul.

Who you really are, is an immaterial soul and the body is an external thing that's sort of an encrustation your soul. So this has important implications for Plotinus' ethics, because his ethics are basically all about encouraging us to turn away from the body and turn towards these higher principles, so universal soul, universal intellect and ultimately the One.

Just the way you might look at a painting and see the painting, and the painting is outside you, so this immaterial intellect would see the forms and behold them, as if they were standing before it. And Plotinus said that that can't be right because it falls prey to sceptical objections.

When you're seeking after bodily pleasure of food and drink for example, this is going to prevent you from doing what you should be doing which is contemplating.

The body is some kind of image of you, it's kind of something that's just attached to your soul, some kind of outside principle, which doesn't really represent who you really are.