Why is God "Father"

Why do we call God the Father? Simply because we have been adopted by Him. When we are a believer we become a child of God, we now receive His care and compassion, we are subject to His correction, we want to conform to the image of the Son of God, we are joint heirs of the Kingdom with the Messiah, we also have liberty through grace, and receive the Holy Spirit.

Oh, but wait a second, I thought we were all children of God because of our very existence. Um...nope. John 1:12 state "as many as received Him, to them He gave the right to become children of God, to those who believe in His name."

Salvation is a free gift of God, there is nothing you can do to earn heaven or be deserving of it, you receive it by faith. Salvation was completed by the Messiah on the cross.

How do you know you have salvation? You'll believe the promises of God. If the Word of God teaches something is true then one believes it to be true. You're life will reflect it and you'll receive the Holy Spirit.