The word "use" usually needs to have something after it:

Do not use this medicine if the seal is broken.

But in written notices, people often leave out certain words that aren't necessary. Here are some examples of similar notices:

Beware of dog

Do not close

Please flush

Falling rocks ahead

Notices like these leave out objects ("this medicine"), "be" verbs ("are", "is", etc.) and articles ("the", "a").