Stain is just a coloring, you will still need a top coat to protect the finish, polyurethane is the most common, available as a gloss, semi-gloss, or satin finish, and requires fine sanding (I use 0000 steel wool) between coats.
I recommend you go and research wood finishing and furniture finishes to see the many options you have and how it’s done.
I usually apply stains with a rag, I find that brushes, either foam or bristles, tend to be harder to get even application with stains.
For the polyurethane do not cheap out on the brush, you’ll regret it later when you find loose bristles in the finish and uneven application.
You’ll also need supplies to clean up, mineral spirits is what I prefer, especially to wipe down the polyurethane after sanding between coats.
Dom