The kingdom of God isn’t somewhere that we go to after we die. The kingdom of God is actually within us. Every believer has the kingdom of God within them and every believer has the power to remit sins because Jesus has given us the power to do so:
You’ll know that the kingdom of God is within you when you heal and cast out demons from people. Before the time of Jesus Christ, no one had the power to cast out demons:
Mark 1:27 King James Version (KJV)
27 And they were all amazed, insomuch that they questioned among themselves, saying, What thing is this? what new doctrine is this? for with authority commandeth he even the unclean spirits, and they do obey him.
Every believer can cast out demons and heal people.
This is why the least in the kingdom of heaven is greater than John the Baptist because of the power that Jesus Christ has given us. John the Baptist could not cast out demons. Note that John the Baptist will in all likelihood be in heaven. Therefore, the kingdom of God Jesus is speaking about is the power of heaven that has been brought to the Earth by Jesus Christ:
Matthew 11:11 King James Version (KJV)
11 Verily I say unto you, Among them that are born of women there hath not risen a greater than John the Baptist: notwithstanding he that is least in the kingdom of heaven is greater than he.
Luke 17:20-21 King James Version (KJV)
20 And when he was demanded of the Pharisees, when the kingdom of God should come, he answered them and said, The kingdom of God cometh not with observation:
21 Neither shall they say, Lo here! or, lo there! for, behold, the kingdom of God is within you.
And this is the power to set the captives free, which every believer has within them so that we can do the things that Jesus Christ did. If we want this power within us, we must die to self and deny our flesh. It starts with surrender. Give up the things you really love and start to deny the flesh.
Luke 9:23 King James Version (KJV)
23 And he said to them all, If any man will come after me, let him deny himself, and take up his cross daily, and follow me.
Once you let the things of the world go and live to please Jesus Christ then you will receive the Holy Spirit because the things of God are revealed by the Spirit of God to those who love him.
1 Corinthians 2:9-12 King James Version (KJV)
9 But as it is written, Eye hath not seen, nor ear heard, neither have entered into the heart of man, the things which God hath prepared for them that love him.
10 But God hath revealed them unto us by his Spirit: for the Spirit searcheth all things, yea, the deep things of God.
11 For what man knoweth the things of a man, save the spirit of man which is in him? even so the things of God knoweth no man, but the Spirit of God.
12 Now we have received, not the spirit of the world, but the spirit which is of God; that we might know the things that are freely given to us of God.