Look up the Web Content Accessibility Guidelines and start looking into how you can get your site to comply with both the level A and level AA criteria. Start with templates first, checking and fixing all of the things that propogate through the majority of the website, like nav bars, common controls, etc. Then break it down by the pages with the highest traffic and the core golden paths through your site. Above all else, you must have an actual blind end-user test out the site along with other people with disabilities using their assistive tech, since then you'll get actual usability feedback rather than being stuck having to assume and doing the barest of minimums to make an experience accessible and usable. Those of us who specialize in this testing do not do it for free.
I made a WCAG 2.1 breakdown that you can peruse plus it has links to the criteria explanations so you can start here:
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