If you do not have a code editor, download VSCode here! (Even if you do, VSCode is probably better than your existing editor so download it anyways LOL)
Figure out a folder on your computer where you'll do all your stuff.
If you think your website will need a lot of interactivity, I suggest setting up ReactJS, which is a web technology that makes coding interactivity a LOT easier. (The GunnHacks website was made using React!) If this interests you, check out this gist.