Ahmed asked which preposition to use to talk/write about an English course and its location. Here are some rules to follow:
Follow the same rules for any kind of course, such as a course in Chinese, biology, engineering, driving, etc.
The following sentences are all good examples of these rules:
I was studying English at Miami Dade College, in Miami.
My sister is studying English in Canada.
Maria is taking an English course at Greenfield College.
Maria is taking a course in English at Greenfield College.
They studied English at a community college.
I have been studying Chinese at a private language school.
I hope this helps.