When you say “know,” this is a type of verb that will show that you have knowledge about something or someone. For example, there may be some details that you need about someone, when you “know” the information, this means that you are aware of what you have to talk about.
When you say “now,” this is a type of adverb. This is something that will be used to describe what is happening presently or what is happening right at this very moment.
For example, when you would use “know” in a sentence, you can say, “I know what she did when she went to the mall.” When you are going to use “now,” you can say, “She is at the mall right now.” These two words may seem confusing but they have totally different meanings.