To save your After Effects composition on a DVD:

Figure 1: Choose the Television standard for your DVD in the New Project Settings dialog box.

Figure 2: Choose File > Adobe Dynamic Link > Import After Effects Composition…

Figure 3: …and then locate your comp in the Import Composition dialog box and click OK to open it in Encore DVD.
The next step is to choose the MPEG-2 encoding settings you want to use. All video is encoded to MPEG-2 for DVD, and you want to use encoding settings that will make your video look its best.
Select the comp in the Encore DVD Project panel, and then choose File > Transcode > Transcode Settings > NTSC DV High quality 7Mb VBR 2 Pass. This preset (which encodes your video to MPEG-2 at a bitrate of 7 megabits per second, doing a 2-pass Variable Bit Rate encode) works well for most After Effects work and is a great place to start with MPEG-2 encoding settings.
Note: If you’re working in PAL, you’ll see the PAL presets in the Transcode Settings menu instead.

Figure 4: Choose one of the transcode presets from the Transcode Settings menu.
Note: If you’re familiar with encoding, you can also choose Transcode > Edit Project Transcode Presets and create your own custom encoding settings.

Figure 5: Add your comp to an Encore timeline.

Figure 6: Set the End Action to determine what happens when the comp finishes playing.

Figure 7: Click the Disc panel to view the disc properties in the Properties panel.

Figure 8: Set the Title Button action using the Properties panel.

Figure 9: Click Burn DVD and Encore DVD renders and transcodes the comp onto a DVD
Of course there is always more than one way to skin a cat. You can also use Dynamic Link to open your After Effects comp in Adobe Premiere® Pro, put the comp on a timeline, choose Window > DVD Layout, and output your DVD from there. If you’re thinking of adding menus or custom navigation down the line, then Encore DVD is a better choice.
You can use the project I just walked you through as a foundation to build on, and quite easily I might add.
For more information on working with After Effects and Encore DVD, see the following resources: