How to refinish just a couple of steps?

What are the steps made of concrete, wood???

https://www.bobvila.com/articles/how-to-repair-concrete-steps/

Hi there,

very lightly sand and re-paint them with the right Gloss Paint if timber. If you are talking Concrete External Steps, use a Masonry Paint.

If they are wood, lightly sand them and restain to match the rest of the steps.

Here's how, take a look at the ref for before and after pictures

How to Refinish Old Wood Stairs

1. Pull any nails sticking out. Remove any trim work where the risers and treads meet.
2. Rebuild any broken stairs or landings.
3. Sand the treads with 60 grit sand paper with the orbital sander, this will take the wood down to the raw finish. Keep sanding with 120 grit, then 150 grit, and 220 grit. We didn’t sand the risers really because we planned to paint them.
4. Vacuum in between sandings.
5. Take a block sander to the hard-to-reach corners.
6. Fill the holes on the treads with stainable filler, let it dry and sand with 220 grit.
7. Do a final vacuum.
8. Install trim work just under where the treads stick out over the risers. We used new “cove molding”.
9. Wipe everything down with paint thinner on a rag.
10. Condition and stain the treads.
11. Apply two coats of clear coat to the treads, following the instructions on the can.
12. Caulk the trim work.
13. Prime the risers.
14. Spackle any holes on the risers.
15. Paint the risers two times with white oil based paint.

ref:https://sheholdsdearly.com/refinish-old-wood-stairs/

Sounds as though your steps are made of wood. If so, you can sand the entire step to remove what finish is still left, find a wood stain that most nearly matches the remainder of the steps and apply it to the newly sanded steps. It may take more than one coat of stain to most nearly match the rest. If the other steps have a shiny seler on them, then also add a sealer to keep the stain from wearing off.

Where are the steps located - indoors, outdoors?

Yes, please post a picture so that we can see what you are working with.

Clean first, then lightly sand and stain to match. Normally steps are only stained without a sealer.

Hi there, this will helps you with a refinish

https://www.youtube.com/watch?v=urii1ChonZQ

Hello. Poly shades might be a product worth your consideration. Here’s a link read over the Q&A and reviews and see if he could be useful for your need. Hope this helps

https://www.amazon.com/Minwax-213704444-PolyShades-Polyurethane-Classic/dp/B001CEN00A/ref=sr_1_4?dchild=1&keywords=Polyshades&qid=1623881920&s=home-garden&sr=1-4