1) create a project
2) change it to a dvd project by clicking the options button within the login area after you make the project.
3) Make it a multi-disc set by editing the project and clicking the link ("make this a multi disc set") near the burn files URL entry field. There is a link there that expands the project form.
4) Enter the urls for each disc.
5) You can choose the type of each disc in a multi-disc set. There are radio buttons that let you choose between audio cd, data cd, and dvd. These buttons are right next to the download URL for each discs burn files.
6) Save the project.
7) Click options and go through the packaging and setup steps to pick the correct packaging and options.
Making both a cd and dvd project combined.