I am a Freshman and i am really nervous for my high school midterms!!! What are some ways to help me prepare?

I have about a week and a couple days until my first midterm! On the first day i have Science then the next day (the ones im most worried for) i have Global Civ. and Spanish!! On the next day i have math and english... Can you please help me with how i should study for Global Civ. and Spanish??