How do you pray for an Atheist or nonbelivers?

I'm a Christian and a lot of people in my family and most of my friends are atheists. I'm asking this from a Christian perspective, how do you pray for atheists? I find myself having an extremely hard time praying for them because I have so much anger against them, which makes me angry at myself. It causes a lot of guilt and shame because I know that I should be showing Christ's love to everyone, but I'm not stepping up to the plate and am doing a horrible job of loving my enemy. Any advice would be greatly appreciated, thank you.