Mossy cement steps?How does one remove moss from cement steps,

Spray with vinegar.

Might be better to put Rubber mat on top ( the sort that allows water and air through, because you are always going to have this problem. There are Moss killers available, but it will be on going....................

You can use Lily Miller Moss Out in the spray bottle hose attachment, you can use bleach and water and a scrub brush, or you can use Wet and Forget.

Be careful with simple coverings... moss can get slippery, and a mat may slide & propel you... I'd do wet & forget or similar... but do NOT forget... scrub the residue after a day, it too can be slick!

Vinegar should kill it

I used to have a brick patio that got slimy with moss every year. I would mix up a large batch of water, laundry detergent, and bleach. Pour some of the mix over the bricks and push it back and forth with a broom. It worked like a charm. The laundry detergent makes the mixture easy to spread and the bleach kills everything. Plus it was very easy to hose off. You could also buy a gallon of Thompson's deck cleaner if you dont have too much area to clean, but you will need a sprayer to apply it. If you use weed killer the smell lingers for months.

https://www.google.com/search?q=NATURAL+MOSS+KILLER+FOR+CONCRETE&ie=utf-8&oe=utf-8

I use a bleach and water mixture, spray and then scrub and then rinse.