There are two ways in which this has been understood.
Some argue that we enter the kingdom in this life when we repent and believe in Jesus Christ. Through the response of faith and obedience, we submit to God’s rule and authority in this life.
Another way of understanding these words is that it refers to the life to come. We will enter the kingdom of God in the future. We receive the kingdom now but we will only enter it in the future1 when Christ returns in glory and the kingdom comes in all its fullness.
15 Truly, I say to you, whoever does not receive the kingdom of God like a child shall not enter it.”