To add to Sarah's comment, a lot of the HTML on your page isn't editable, so if you're just trying to edit your profile's visual styling, you should check out w3schools'
css tutorials. You should learn about both, but if you want something more immediately applicable to your profile, CSS might be a good starting point
edit: also, don't be overwhelmed by the amount of stuff in any of these tutorials. You don't need to memorize everything. I do software development for living and I don't think I've ever worked on something without having some kind of reference open in another tab, lmao