What can I use to cover hardy board in the shower?

At this point you can install tile or stone. Which do you like better? Which would look better with the style of the home?

https://www.jameshardie.com/products/hardiebacker-cement-board

I used tile plank flooring it was cheaper than regular shower tiles

Make sure you've filled in the seams with mortar not drywall mud .

Once the hardie board is up, you'll use fiber tape specifically for bathrooms and mortar

https://homedepot.sjv.io/c/1285430/456723/8154?u=https%3A%2F%2Fwww.homedepot.com%2Fp%2FSaint-Gobain-ADFORS-Alkali-Resistant-2-in-x-150-ft-Self-Adhesive-Mesh-Cement-Board-Tape-FDW8691-U-FDW8691-U%2F202251875

Once that's done then you'll want to waterproof the hardie board. After that's dry, then you're ready for tile. You'll use a thinnest to set the tiles, tile spacers to keep the grout lines consistent with the pattern. After everything is in place, you'll grout and when that's done, you'll caulk any corners or seams where the tiles come together.

If you have any questions, the people at the home improvement store are also a wealth of knowledge.

Octavia, here are some videos that will walk you through the whole process. Sometimes it helps me to actually watch someone do the job I'm trying to accomplish.

https://www.youtube.com/results?search_query=hardy+board+in+shower

Hardy board is an underlayment for tile installation. It's not meant to be on the surface. You need to seal seams, corners, and then install tile over it. You have half of the job done.

Hardy or backer board is used in areas where there will be a lot of water or moisture over a long period of time such as in a bathroom shower stall or adjacent to a bathtub. Now that the hardy board is installed, it's time to install tile using mastic to attach and the grout between the tiles and then sealant applied as well as caulk to seal off moisture from around the edges.