After quoting Psalm 68.18, that prophesied of Jesus ascending on high and giving gifts to men, Paul then explained,

(Now this, “He ascended”—what does it mean but that He also first descended into the lower parts of the earth? He who descended is also the One who ascended far above all the heavens, that He might fill all things.) (Ephesians 4.9–10).

To say that Jesus ascended means that He first had to descend, descend to this Earth, and then descend into the Earth when His friends buried Him after His death.

Then He arose from the dead, and eventually ascended back to heaven, that He might fill all things, that is, fulfill all things said about Him.

Jesus is Lord. Jesus is the Lord you read about in the Old Testament, unless the passage makes it obvious that it is a reference to the Father.

Do you know just who Jesus is?