John 16:23

In that day you will not (need to) ask Me about anything.  I assure you and most solemnly say to you, whatever you ask the Father in My name (as My representative), He will give you.

Our faith in Jesus Christ gives us the authority to use His name.  We have the stamp of Jesus on us and inside us, and that makes the devil tremble.  Our part is to ask in faith and not doubting that what we ask for in His name will come to pass.  Faith or believing being fully convinced that God is willing and able to act on our behalf.