Just remove the black tape and the screen protector that's built in for the Mars 3. I got a replacement screen protector from here: https://smile.amazon.com/dp/B09W61FB9C?psc=1&ref=ppx_yo2ov_dt_b_product_details

I also had a thread about my issues a few weeks ago, very similar situation, and I posted some pictures. edit: https://www.reddit.com/r/ElegooMars/comments/u9upd6/screen_protector_on_mars_3/