No one except God and the Theotokos are in heaven, as far as I'm aware, since the Theotokos was assumed into heaven. Elijah and Enoch are both probably hanging out somewhere on Earth or otherwise somewhere else. They were not assumed, but translated, taken away by God, usually interpreted to be in preparation for the Second Coming of Christ, as they did not taste death, and so are the two witnesses of Revelation.

All the rest are in Hades or Sheol, which is basically a pre-Second Coming holding cell, full of the best saints and the worst sinners, each experiencing things differently. The saints receive a foretaste of paradise, while the unrepentant receive a foretaste of hell. We pray for those who are not saints because our prayers can help their condition in Hades.

At the Second Coming, there will be a general resurrection, that is, anyone who has ever died will rise bodily from the grave, including the saints.