HOW THE devil DO YOU CODE YOUR HOMEPAGE

i took some dooky fart coding tutorial for trying to make a custom tumblr theme however many years ago. but it sucked really bad :( all i remember is you open a prompt or something with brackets + prompt and then you close the prompt with brackets + / + prompt. i think i can get by with minimal text editing (like making text italicized or bold) but idk how to do much else visually.

anyway this isnt too serious of a question but if anyone has any good tutorials feel free to let me know :)