We're going to make this in iPhoto so I'll launch it. I've already created an album of images that I'd like to include in my slideshow. I assume you know that to create an album you select images somewhere in your iPhoto library and choose File > New Album to create an album of your own.
The dead simple way to approach this is to to just click on the Slideshow button at the bottom of the window. This will produce the theme chooser. From this chooser you can select a holiday template. The slideshow will play so you can see what you're in for.
But within this chooser you can modify the slideshow. For example, you might want music other than Vince Guaraldi--great as that is. You do that by clicking on the Music tab. You can also choose how long each slide will play. This is done within the Settings tab, where you can also choose different transitions. Once you're happy with your slideshow you can then export it using the Export command found in the File menu.
The other option is to use the Share button at the bottom right of the window. From here choose Slideshow. On the resulting screen you see a title for your slideshow. You can edit this to something more appealing by double-clicking on the title.
Also, at the bottom of the window you'll find controls for themes, music and settings, similar to what you saw in the theme chooser.
You'll also find that you can insert a text slide if you like. Just choose an image that you'd like to attach some text to and fill in the blank.
When things are put together to your satisfaction, click the Export button at the bottom of the window. Choose the output format for your slideshow--480p, 720p, or 1080p. Note that the higher resolution you choose, the larger the resulting movie will be.
And that's all there is to--easy steps for creating a slideshow that you, your friends, and family will love.