2 witnesses of Christ here, and 2 further echoes from the reading.
But we believe that through the grace of the LORD Jesus Christ we shall be saved, even as they. Acts 15:11
Peter settles the argument: Jews and Gentiles are saved the same way, through the grace of Jesus Christ. Keeping the law of Moses does not save anyone; the Savior does.
How we know: the verse itself names Him · a Church study aid lists it
Simeon hath declared how God at the first did visit the Gentiles, to take out of them a people for his name. Acts 15:14–17
God gathers a covenant people out of the Gentiles who carry His name. Latter-day Saints understand that the covenant name the Lord's people take upon them is the name of Jesus Christ.
After this I will return, and will build again the tabernacle of David, which is fallen down; and I will build again the ruins thereof, and I will set it up: Acts 15:16–17
James quotes the Lord (Jehovah) through Amos, promising to raise up the fallen house of David and bring the Gentiles in. The early Church saw this fulfilled as Jesus, the Son of David, gathered Gentiles into His kingdom.
Men that have hazarded their lives for the name of our Lord Jesus Christ. Acts 15:26
The council's letter praises Paul and Barnabas for risking their lives for the name of Jesus Christ. Loyalty to His name was worth more to them than safety.
How we know: the verse itself names Him