Albert Barnes Commentary 1 Kings 1:39

"And Zadok the priest took the horn of oil out of the Tent, and anointed Solomon. And they blew the trumpet; and all the people said, [Long] live king Solomon." — 1 Kings 1:39 (ASV)

The tabernacle - This was probably the one David had made for the ark of the covenant on Mount Zion (2 Samuel 6:17). The holy oil was part of the regular furnishings of the tabernacle, as shown in Exodus 31:11 and Exodus 39:38.