Drawing a mind map is as simple as 1-2-3:
Start in the middle of a blank page, writing or drawing the idea you intend to develop. I would suggest that you use the page in landscape orientation.
Develop the related subtopics around this central topic, connecting each of them to the center with a line.
Repeat the same process for the subtopics, generating lower-level subtopics as you see fit, connecting each of those to the corresponding subtopic.
Some more recommendations:
Use colors, drawings and symbols copiously. Be as visual as you can, and your brain will thank you. I’ve met many people who don’t even try, with the excuse they’re “not artists”. Don’t let that keep you from trying it out!.
Keep the topics labels as short as possible, keeping them to a single word – or, better yet, to only a picture. Especially in your first mind maps, the temptation to write a complete phrase is enormous, but always look for opportunities to shorten it to a single word or figure – your mind map will be much more effective that way.
Vary text size, color and alignment. Vary the thickness and length of the lines. Provide as many visual cues as you can to emphasize important points. Every little bit helps engaging your brain.