How can I fix a crack in concrete steps?

Answer 1

Go to Lowes or Home Depot, or I suppose any hardware store, and but a squeeze bottle of concrete repair.
All you need do, provided the crack is small, is squeeze the mixture in the crack, and smooth it out. Make sure, it's the same color, usually a grey color, for a better match.
If the crack is bigger, you may need the box, of concrete powder, where you have to add water, to make up a paste. Directions on the box.
Just ask them at the store, they will point you right to the products.

Answer 2

Buy first a cement repair tube.

Then clean up the crack.. usually, you have to wet the crack on the concrete steps and then apply the cement repair.