I'm not gonna go through the steps of painting a wall. For one I'm no expert and two, it's pretty easy to figure out. You can buy a little can of chalkboard paint for $10 at Home Depot and that's enough to give a small wall two coats.
I will say that the taping is the most important part so make sure it's on really well.
Your hands will look like this afterward.
chalkboard wall diy