If you pick a long wash cycle then it will flush soap into the washing drum from all three segments in sequence from left to right. The last segment is set up as a reservoir so I think they expect you to put a liquid in there.
What I would do is put soap powder in the first two segments and fabric softener in the last one.
But sometimes the skin soap in the bathroom is the size of a coin and hard to use, if the soap is like that I will put it in the first segment of the washing machine, then I will put powder in the second segment and I will put cheap perfume in the third segment. The £ shops sell perfume for £1, I would put that in the third segment to make the clothes smell nice.
I don't like those all in one power pod things that you just put directly into the drum; I'm just set in my ways. I have my own way of doing things and don't like like changing my habits.
Did I mention that most people find me very boring in this world, I'm not exaggerating.