Tensorflow abstracts a lot of complicated concepts. The best way to learn Tensorflow then, is to learn the concepts, try to implement those. Then when you go to the Tensorflow APIs it's easier. After doing this, you can use a lot of resources available to you. Books, articles, youtube videos. Check out Siraj Raval's channel on youtube. He does a lot of videos on ML/DL and uses Tensorflow in some of his videos.