This is a simple step once you get into it.
There are many ways to do it. I envision your shelving to be less than 3/4" thick. Small medicine cabinet shelving might be only 1/2" thick.
Small little moldings are sometimes called Beauty Molds.
They are made to cover the edges of plywoods or used as decorative trim.
You can make your own or buy ready-made beauty mold.
Pine is probably the most popular. This molding is sold in solid wood or plastic.
If you're painting it won't matter, but of course the plastic type won't accept a stain.
If your mold is wider than your boards edge, center it, glue it and then plane down flush after it dries.
If you don't have time to do it right the first time, when will you have time to do it over?