Critical thinking is not a matter of accumulating information. A person with a good memory and who knows a lot of facts is not necessarily good at critical thinking. The first step to critical thinking is to understand how your biases and/or prejudices may unfavorably affect your decision making.
Critical thinking requires metacognition and System 2 thinking. Explore Daniel Kahneman's best selling book, "Thinking, Fast and Slow" in which he discusses System 1 & 2 thinking.