1. Read: read a book on the topic. Not any book. Read a book written by someone who is an expert on the topic and has a genuine gift for explaining things clearly.
2. Implement: write software that implements the topic you are learning, or solve a bunch of problems relevant to the topic, or write a paper on the topic.
3. Teach: create a bunch of Powerpoint slides along with a bunch of lab exercises and then go share your knowledge with some people.