The particle で (de) is used to express two things, a place where an action occurs or a means. Note the difference between で and に (ni) which on the contrary is used to indicate a place where nothing happens.

To use で to indicate a place you must use the formulation: place + で, note that で will be used with action verbs unlike に which is used with state verbs.

がっこう で たべます (I eat at school). Here the school is the place where the action occurs で therefore follows the word がっこう (school).

To indicate a means we will use the formulation means + で for example: わたし わ くるま で がっこうにいく (I go to school by car). Here くるま (car) is the way to go to school (がっこ) で therefore follows the word くるま.