I'm not sure what you're asking, but I'll try to help. "Right now, I'm at a concert." This is correct because you are physically somewhere (your body is standing/present at a concert). "I'm on italki, and I'm usually on Skype." This is correct; use "on" for technology and sites on the internet (there it is again, on the internet). "I'm in a meeting, so I can't answer my phone. I'm in my office." You can use "in" for a room that encloses you, or for a meeting. Hope this helps.