You don't really need to get into it unless you want to. If you're not logging in to Steemit using your posting key only, using your password to update your avatar image isn't too much different. If you're interested in learning more about the Steem CLI though, I made a guide to get you started: https://steemit.com/steemhelp/@pfunk/a-learner-s-guide-to-using-steem-s-cliwallet-part-1