You can change your subjects 1 of 2 ways.The first way is to click the 3 lines in the top right corner. From there select Account Settings from the dropdown menu.
Updating subjects this way will take you through the account setup process again.
Account Settings for the Dropdown Menu
You can also change your selected subjects from any feature page — such as Questions, Syllabus, Performance, or Insights. In the top left corner, you’ll find a dropdown showing your current and selected subjects. At the bottom of this list, click Edit Selected Subjects.