Hello, I am in my second year (Anthropology) but in my first year i failed a course that was not a prerequisite. I was not able to take summer school going into my second year because i couldn't afford it so i'm going to take the course this summer. My question is do i need to retake that course in order to get the credit or can i just take any course to fill it up. They do not offer the course this summer.

Why don't you read your academic requirements in the student calendar to figure it out?

If the course is not a prerequisite for anything, you don't need to retake it. You can take any other course - all that matters in the end is that the required courses for your program are met, and the amount of units required for your program (including electives) are met.

If the course is required for your program, even if it's not a prerequisite for another required course, then you would still need to take it obviously.
It just comes down to whether or not you need that course for anything.