The 不知…好 structure is used when a speaker doesn’t know how to do something or is not sure how to do it better. For example, "I don’t know how to put it better".
A verb phrase, which consists of a question word and a verb, is placed in the middle of the structure in place of the ellipsis.
A complement can be placed after a verb.
They have so much money they don’t know how to spend it