Most people who get this wrong write "is comprised of", and they are in enormous company. It is so widespread that several major dictionaries now list it without comment. Careful editors still treat it as an error. Which puts you in the odd position of following a rule that is losing, in front of readers who may be the last people enforcing it.
A verb. To consist of, or be made up of. The whole comprises the parts — and it is never followed by "of."
A verb. To make up or constitute. The parts compose the whole, and "is composed of" is correct.
Quick way to remember
Put the whole first and use "comprises" with no "of." Put the parts first and use "compose," or turn it round as "is composed of." If you find yourself typing "is comprised of," swap in "is composed of" or "comprises" and the sentence is safe.