Add a page on squarespace

I need some pages added/edited to my website as i am now providing prescription lenses as well as spectacle frames and wondering if this is something you can help with. My website is [login to view URL] Essentially it should be an additional page after selecting the frame and adding it to the basket where a prescription is entered or uploaded by a drop down selection box and some extra options with prices before heading to the checkout. Here are some examples: Warby Parker [login to view URL] Viu Eyewear [login to view URL] Bailey Nelson [login to view URL] Ollie Quinn [login to view URL] once the frame has been added to the shopping cart, it should take you to a page to select frame only or with prescription. If you select with prescription it will automatically add $50 and then you have the option of choosing extras such as 1. Thin Lens 2. Photochromatic lens 3 Blue blocker Or a combination of the above for additional cost. There should be extra information about optical measurements etc as well which i provide the literature for. It should then be put in a basket all together under 1 item for checkout.