3rd Heaven of course is at the throne.

2nd Heaven is where Satan roams to and from 1st heaven. Remember he was cast out of 3rd heaven at the fall as the most beautiful angel (Lucifer), one of the 24 archangels, but in the Great Tribulation he is cast out of 2nd heaven to the earth (Rev. 9.1).

1st Heaven is earth and the universe where matter and anti-matter exist.
No one is in 3rd heaven yet except Christ, not till first rapture takes place (Rev. 7.9).

Then Christ returns to meet the saints in the air (2nd heaven), and then He returns with His holy myriads to earth-1st heaven (Jude 14,15).

Very simple. Some have been raptured already, but not to 3rd heaven, because we are to receive our newly clothed spiritual bodies together at the consummation of this age according to 1 Thess. 4.15-17.