The way you "rest" in the finished work"....is to understand what it is.
For, how can you tell what you dont know, or how can you understand what you dont understand.???
So, the wonder of Salvation is how simple it is, because its not designed to confuse or to endure.....its designed to be received and free you.
So, think of it like this..
You are on an island, and God is in heaven, and between you and GOD is your sin., which is a barrier that separates you from God.
So, what do we do about that?....How do we solve that????....How do we get past the sin barrier so that we can be with the Father God, forever?
Well, we cant do it by ourselves., and the reason we cant is because there is nothing we can do to GET RID of that sin barrier., nothing we can do of ourselves, to eliminate the barrier.
Its exists because we exist.
And THIS is the reason that many cant find rest, cant find relief, and cant find salvation, and its because they have not realized that their sin is a lifelong situation that they cant ever resolve by anything they can do.
Nothing.
And God, realizes this, and so He created a method.... a means....... a WAY.... that our sin can be removed completely and forever so that its no longer a barrier that keeps us apart.
In John 14:6, you read this.......Jesus speaking....."I am the WAY....."
And THIS is what God has provided as the only means to get our sin barrier removed completely and forever, and THEN we can have our REST.
So, enter now the CROSS and Jesus upon it.
THIS is how God is taking away our sins.....Its by allowing Jesus to die for them all......and this is the "WAY" that Jesus is speaking about.
Jesus is the WAY, and Jesus on the CROSS is the WAY.......and so, this is how we remove the sin barrier.....WE let Jesus do it for us on a Cross.
We hear this Gospel message, and then we believe, we trust, we accept that we cant take care of our own sins, but we TRUST that Christ can because He said He alone is the WAY, and God said that if you will BELIEVE THIS and TRUST THIS from your heart, then your sin will be removed and you will become God's own child the very instant you believe-trust.
And the REST that we are to enter into, is the assurance that we can trust Jesus and God to take care of our salvation, and to keep it for us, and to never let us go.
We are to REST in this knowledge, in this assurance, that God through Christ has established us as worthy to belong to them, forever.
See, Salvation is simply God through Christ's blood making us worthy to be accepted, forever.
Thats all it is......and its as simple as that.
The REST is when we stop worrying about how WE are to make ourselves worthy enough for God to accept, which is impossible and instead just REST in the assurance that JESUS HAS made us worthy.
And when a believer comes to this understanding and realizes it and TRUSTS that JESUS has taken care of all that is necessary for God to accept us, and that for Eternity, then the believer has entered into the REST of God via the finished work Christ on the Cross.