How can Jesus rule the earth during the second coming, if he is only in Jerusalem? I don't understand, how Jesus comes down in the clouds and rules on the mount of olives, how can the people in other countries see him? I know the clouds all will see him, but once he actually steps on earth, how will I see him or be with him? Do we all go to Jerusalem?
Put aside the question of whether the Jerusalem which Jesus will enter and rule from is:

1) The Jerusalem we know (but fixed up)

2) A new physical city that descends fully built from Heaven, as described in Revelation

3) An image of the Church, where the people of God are the walls and buildings to be inhabited.

How can Jesus be seen by the world?

1) Television and the internet, via TVs, cell phones, tablets and watches which are in the possession of most people today. 

2) Supernatural means. If man is capable of creating the internet, God is capable of even greater marvels.

How can Jesus rule the world?

1) Delegation. At his disposal, Jesus has:

a. angels. Matthew 26:53 says:


  Do you think I cannot call on my Father, and he will at once put at my
  disposal more than twelve legions of angels?


b. the church, whom he promised will judge the world. The apostles will sit on thrones. 1 Corinthians 6:2 says:


  Or do you not know that the Lord’s people will judge the world? And if
  you are to judge the world, are you not competent to judge trivial
  cases?


Luke 22:29-30 says:


  And I confer on you a kingdom, just as my Father conferred one on me,
  so that you may eat and drink at my table in my kingdom and sit on
  thrones, judging the twelve tribes of Israel.


2) Action at a distance. In Matthew 8, Jesus heals a centurion's servant while that servant was sick in bed miles away. He does not need to be physically present to accomplish the Father's will.