The two witnesses are the two olive trees and two candlesticks. The meaning of the two olive trees and candlesticks are found in Zechariah.
Zec 4:2 And said unto me, What seest thou? And I said, I have looked, and behold a candlestick all of gold, with a bowl upon the top of it, and his seven lamps thereon, and seven pipes to the seven lamps, which are upon the top thereof:
Zec 4:3 And two olive trees by it, one upon the right side of the bowl, and the other upon the left side thereof.
Zec 4:4 So I answered and spake to the angel that talked with me, saying, What are these, my lord?
Zec 4:5 Then the angel that talked with me answered and said unto me, Knowest thou not what these be? And I said, No, my lord.
Zec 4:6 Then he answered and spake unto me, saying, This is the word of the LORD unto Zerubbabel, saying, Not by might, nor by power, but by my spirit, saith the LORD of hosts.
The two olive trees are the word of the Lord that speaks to Zerubbabel. The two witnesses are the bible, 1) Old Testament 2) New Testament.
The candlestick is described in detail in the book of Exodus. The candlestick has exactly 66 knops, bowls and flowers.