How to use Base64 Encoding in HTML Website to add a Password to access site

Question

So I have a site where I put my music and where I also Review music, Just for fun. I Added an ARG That's apart of my album and basically I want people to find the code hidden in the album, Go to the website and enter the code to access bonus tracks and songs that are unreleased. Atm You can literally just inspect element and see what the Code to enter the site is, but I Want to fix that. I asked someone that was able to do what I want to do and he said he used "Base64 encoding and stored it in a JS Array, When the user inputs something he used an atob() function to encode the input and check if his password array contains the same string." I have no idea how to do that, I'm very much a beginner with coding such so please explain this to me as if I am an idiot. Not too far from reality.