how to lead someone older than me to Christ

[Never thirsty!]

he's 23 and I don't know what his religion is but i know he isn't a Christian he told me he doesn't believe in God or angels or Hell and he is like a brither to me so I don't want him to have to suffer damnation neither do i want to be seperated from him forever he's one of the only people outside of my family who don't look down on me because of my disability and i know no one does that in heaven but heaven isn't a place where that isn't the norm so it feels like something about me other than my disability stands out to him so i don't have to try and act like nothing 's wrong because he doesn't see anything wrong which has had a huge impact on my mental health i've been able to keep from cuttting for the whole month when i used to be lucky to go one day· I honestly dont want to go up to the throne and ask God "did A· D· make it" and him say "no" it would be my fault then because I had a chance anf stood on the sidelines i don't want that

[drill]

I would suggest that you pray for him whenever you can. Also, don't be discouraged if you don't think that you see progress right away, as that God works in mysterious ways. Have you tried inviting him to church? Or possibly just bringing up something about your faith when you find the opportunity to do so. No matter how you handle it, prayer is always the best way to go about this, as you are giving this over to God and knowing that in His strength that all things are possible. Finally, be patient, I have known several people pray for their spouse to become saved and it taking several years for them to come to the Lord.

[ClaecElric4God]

The same way you lead someone younger than you to Christ. I mean, obviously you address them differently and generally with more respect, but it's ultimately up to God.
Drill hit the nail on the head, er, the screw I guess. Prayer is the biggest thing. We Christians don't put enough stock in prayer. We treat it like a side thing that you do when something really big comes up or whatever. But prayer is an integral part of every aspect of our lives. As much as you want to see your friend saved, nothing you say or do will do any good if God's not in it. You need to pray that God would work in his heart and life and bring him to the point where he's ready to hear the gospel and accept Christ.
As well as praying for your friend, you need to pray for yourself. Pray that God can use you to lead your friend to Christ. Pray that God will speak through you. Because I can tell you this, one of the best ways to mess it up is by saying something that you may think will be helpful, but is totally out of God's will. Speaking with our heads quite often does more harm than good. Spend time praying, reading your Bible, and getting closer to God, so that He can use you.
And like drill said, try inviting him to church. It's always good to get people under the preaching of the Word of God.
Oh, and another thing I can't believe I forgot: Christian testimony. Make sure your Christian life is showing! We are the light of the world, and it's by seeing Christ through us that people often get the desire to have what we have. A lot of people get turned off by a Christian who acts like a jerk, a bum, or a loser. Don't let people stereotype you as another judgmental, holier-than-thou Christian.
I'll be praying that everything works out and your friend gets saved. I hope I helped some!