This is a great question. Now that my kids are older, I’ve had people asked me how I raised them to know who they are in Christ. Honestly, I don’t know that I had a "plan" when they were younger. But I did endeavor to LIVE my faith before them. In other words, they saw me ask for forgiveness (even to them when necessary), get up early and read my bible, show kindness and respect to them and others, etc. So it’s important to understand that if they see their parents acting one way at church and another way at home, then one looks like a mask (hidden identity). So be transparent.
But also, listen to the things they say, especially about themselves, and correct it quickly. If your child is struggling in school and they comment that they are dumb and can’t do the work, be sure you tell them what GOD says about them: "You can do all things through Christ… You are not dumb, you are wise because you have the Holy Spirit as your helper…" etc. Help them change their words because we have what we say (Mark 11:23).
And lastly, I’m a strong believer in putting them in front of their mirror so they can see themselves the way God already sees them. I’ve done this individually with each of my kids. God did it with me and I wanted my kids to know their mirror is not the enemy.
Hope this helps!