"Tous disent : impose-toi !"
Yes, it means "don't be shy, be brave, express yourself, be convincing..."
The translation should reflect that then. As it stands "Everybody says: impose yourself" is seriously incomprehensible for an English speaker like me!
Impose yourself is very rarely used because it often has a negative connotation. Not sure exactly when it is it used in french, but I would suggest "don't be shy" in English as a commonly used equivalent.