According to Moses, God told the people to put a special cover called the "mercy seat" on a box called the "ark" in the holiest part of their meeting tent. This was a way for them to feel close to God and know that He was with them.
Exodus 26:34: And thou shalt put the mercy seat upon the ark of the testimony in the most holy [place].
Exodus 26:34 instructs that the Ark of the Covenant should be behind the veil, but Hebrews 9:3-4 places the golden censer there as well, suggesting a different arrangement.
Hebrews 9:3-4: And after the second veil, the tabernacle which is called the Holiest of all;