Measure the case you will be using with your disk. If there is artwork or a placeholder paper cover in the case, remove it and measure that. If not, cut paper and test it to see if it fits and readjust if necessary. Use the measurements of the final paper that fits as the measurements for your cover.
Design the cover and decide how you will print it. Your method of printing will decide whether you can use color and how much. If you are going to use your computer printer to print several hundred copies, you will save ink by designing a cover that doesn't use a lot of ink, for example.
Launch the software that you will use to create the CD cover. If you have a template, open that. If not, re-size your page to make it the size of the CD cover, or mark off the measurements on a larger page so that you create the right size cover. Your printer will print the document on a standard paper, unless you cut the paper first, so don't worry if you can't make your page that is the right size, as long as your final document can be cut to fit the CD case.
Place any images on the page first. Most software has a tool that lets you add an image to your document. Re-size the image until it's the size that you want.
Add text. Your CD cover needs a title, unless the image contains the title. Type any other text you want. If you are making a cover for a CD jewel case, you will be making the front cover only. The back of the paper will be visible when you open the case and you can put text and images on that side, too, by making a second page or a separate document. If you are making a cover for a taller, DVD-style case, you will make one piece of paper that is both the front and back covers and the spine as well. See your measurements to determine where the front cover stops and the spine starts. Use a text rotation tool to put text on the spine, reading sideways.
Make a test print. Cut the test copy and insert it into the case to see how it looks and make sure that it fits. Make adjustments as necessary.
Print the final copy or copies of your cover artwork.