Most of the theme options you can find on the theme settings page in your dashboard. As an example we use the theme Frau, so the page in the dashboard for us will has the same name. You can get access to this page using left menu of your dashboard.
Each option of the theme settings has detailed description right in your dashboard, so we will not talk about each option here. Instead we will talk about sections.
Take time to read descriptions of each option you are going to change, and you won’t make mistakes.