Select the images you want to use. Tone them in photo manipulation software such as Adobe Photoshop, iPhoto or iMovie. Resize them to 72-dots-per-inch resolution since this is the standard for images on a screen such as a television or computer.
Choose the music and digitize it. If it is analog---if it is from a record or tape---you must connect a converter between the source and the computer. You can record the music with basic software---some of it freeware or shareware on the Internet---and then compress it to mp3 using the Import feature of iTunes. The music will be in iTunes for ready import later. If you wrote the music, you can use it anywhere. If you are choosing someone else's work, you can't use it to make money and you should give credit somewhere in the slide show.
Open iPhoto for a basic musical slide show. iPhoto is part of the iLife suite of software packages from Apple. You can copy images there by going to "File>Import" to library for images already on the hard drive, or you can upload images directly from a digital camera. Once the images are in iPhoto, create a new Album with the "+" on the bottom left. Name the album, then go back to the Library and select the photos you want in it. You can "Shift-Click" for contiguous images or "Command-Click" for noncontiguous images. Drag them to the new album. This will be the basis for the slide show. You can reorder the photos by dragging and dropping them.
Add the music by selecting it from iTunes. Go to the "Play" button in the lower left of the screen. This will bring a pop-up menu where you can both change the flow of slides and choose the music. Click the "Music" button at the upper right. This will show options for song locations. There are some prerecorded pieces, or you can go to iTunes for your own selections. Choose "iTunes" and find the song. Click on the song, then click the "Play" button in the lower right. The music automatically will loop around if there are more images than music. Conversely, the music will fade off if it is longer than the images take to project.
Go to "File>Export" and you can save the slide show as a QuickTime movie that will play for anyone with the free QuickTime program. You can burn a disk of it or, using iDVD, you can burn it to a DVD.