If you start working on your cover and booklet artwork only today, then you're definitely late. It's always a good idea to start thinking about your cover while working on your songs already.
Just as with your recordings, it will be very important to get help if needed.
If you're not a talented visual artist, then find a friend who can help you out, or hire a professional artist or a designer. If you don't know how to create a professional layout, then ask a friend who's working in the media business, or look for a media agency or an expert who can do the job for you.