It is that easy. We receive Jesus Christ, we believe in Him and what He has for us, and we are given the right to become heirs in heaven with Him.
“12But to all who did receive him, who believed in his name, he gave the right to become children of God,” — John 1:12 (ESV)
The opening sentence of our introduction to the book of John in my ESV Bible is: “The Gospel of John was written to persuade people to believe in Jesus (20:30-31).” Verse 12 above speaks more to this and what we get in return for doing so, adoption.
It is on us/me to do what is required to get adoption. But it is not what is generally thought. We do no earn our way. We do not take on more work and perform at a certain level. The requirement is only to receive Jesus for who He is and believe in Him. When we have done these tow things, we get the reward, being adopted as children of God.
What are you doing thinking it is getting you somewhere? Are you out there working on being good and doing good things to earn your place in heaven? What if you put down your works and received Jesus and believed in Him to get the reward?