New to aneros need help to generate a p-wave?

what I want to know is what type of breathing should I do
Any type you want. I find the session steers my breathing, and not the other way around.
and should I need to be erected or aroused to achieve a super-O?
Erected? No.
Aroused? That depends.
The understanding I have of arousal has changed over the years. I never really thought about arousal beyond "I want to cum". But it's more nuanced than that. Maybe the kind of arousal I look for now, is more like "I feel sexy and want to be held". I think as you become more re-wired, the other facets of it become more noticeable. I think it's a difficult thing to nail down, but I've gotten better at noticing when I'm in the mood for the aneros specifically.
And what techniques should I do to achieve a p-wave for beginner to anal?
It's not really a 1:1 mapping of action:reaction. Some things work some times, and not others. I think a large part of it is being able to feel your way into a session and ride along with what wants to happen, when it wants to happen. Techniques are a great way to explore, but at some point you have to switch off the analysis and let the wave carry you helplessly into some other sensation. It's really counter-intuitive to everything we learned from penis masturbation, where gripping tighter, pumping faster and focusing more ferociously is what you do to get off the launch pad.

And what ever you do, don't get frustrated by not finding the right technique, because it isn't all technique. When I first started out, my prostate wasn't nearly as responsive as it is now. Some people don't believe "re-wiring" is a thing, but from my own experience, I think it is. I think there's a lot you get "for free" over time and with practice. So have patience and enjoy the journey.