In Job 1:6-9 it says, "Now there was a day when the sons of God came to present themselves before the LORD, and Satan came also among them. And the LORD said unto Satan, Whence comest thou? Then Satan answered the LORD, and said, From going to and fro in the earth, and from walking up and down in it. And the LORD said unto Satan, Hast thou considered my servant Job, that there is none like him in the earth, a perfect and an upright man, one that feareth God, and escheweth evil?"
The Bible shows that the serpent, who is known to be the devil, was kicked out at the time period of Adam and Eve sin and wasn't allowed back. If so, why in Job 1:6-9 Satan was in heaven? The reason I assume that Satan was in heaven came from his reply when God asked him where he came from. He said he came from going to and forth in the earth. It is proven that this must have transpired after the situation with Adam and Eve when they were kicked out of the Garden because God asked Satan if he has seen Job and surely Job was born way after Adam and Eve's time.
The book of Job mentions the flood (Job 22:15-16), so it was written long after the Creation. Most place it in the same era as Abraham.
Yes, the Bible mentions that Satan was kicked out of heaven (Revelation 12:7-9), but it never states that this happened at the beginning. Instead, it appears in the context of the founding of the church. See "When did Satan fall?" for more information. There was a period of time when Satan was allowed access to heaven.