Tumblr: I can't seem to customize the size of my title, or any text size, or even the size of the icons in my following section. Anyone care to give advice?

Tumblr offers easy customisation interface! On when you log in, go to
tumblr.com/dashboard
click on preferences icon on top right
there, there is a button called Customize Blog
Once you click it, you will get a menu with options-> Info Theme Appearance Pages Advanced
In Appearance option, you can change the color scheme of your blog.
Remember to click Save button after you have finished making changes.

These easy customisation options depend on the theme you have chosen.

If you want to do more of customisations other than the options offered for your current theme, you can go to Theme> Use Custom HTML and then work with the HTML for changing font and so on…

Well neither of those answers helped. I thought it was made obvious that I had already checked the available customization options before asking for help. And I apologize for linking my Tumblr account; I’m new here.