It is an invariable particle which precedes the verb it modifies. So for example the following sentence:
pile qappakas
[pi.'le qa.ppa.'kas]
I eat fish.
Turns to:
pile wan qappakas
[pi.'le waŋ qa.ppa.'kas]
I need to eat fish.
Just as easy. The question now is how to create a sentence of the likes of "I need you to eat fish", in this case we would change the flow of the verb (the suffix) but include a pronoun with topic marker preceding the particle. So:
pile ikejen wan qappadas
[pi.'le i.'ke.jen waŋ qa.ppa.'das]
I need you to eat fish.
I need you to eat fish.
The meaning here that it is one's need that the other person do the action, note that the flow is quite simple "you eat fish", and the pronoun would be modifying the particle, the needing of something. So it is my needing that you eat it, or "to my mind it is needed that you eat it".
arejen wan osha tanakash
[a.'ɾe.jen wan o.'ʃa ta.na.'kaʃ]
I think he needs me to speak to them.
I think he needs me to speak to them.
This one is more complicated, but the analyses is the same. It is his need / I speak (to) them. The transition of the verb marks a flow from a 1st person singular to some other person, which is being explicitly marked by the pronoun "osha" (they) in this case.
A simple lesson for today and one more particle to get to know.