In verse 1 John is called up into heaven which represents the rapture of the church. As verse 2 starts he says immediately he is in the spirit and for him to be able to see what he is going to be shown he has to be in the spirit because of his physical condition. He had been boiled in oil and his eyes had been removed, so this lets us see if we let the spirit guide us God can allow us to see the things we need to see.
Revelation 4:2 And immediately I was in the spirit: and, behold, a throne was set in heaven, and one sat on the throne.
3 And he that sat was to look upon like a jasper and a sardine stone: and there was a rainbow round about the throne, in sight like unto an emerald.
4 And round about the throne were four and twenty seats: and upon the seats I saw four and twenty elders sitting, clothed in white raiment; and they had on their heads crowns of gold.
5 And out of the throne proceeded lightnings and thunderings and voices: and there were seven lamps of fire burning before the throne, which are the seven Spirits of God.