Hi,
There are some available guides regarding creating a project using S32DS. Below will be a link redirecting to these HOWTO's.
S32DS - list of HOWTOs - NXP Community
As to integrating other files to your project, you have to create the correct links in order for your project to be able to see them. This can be made manually from the project properties.
Also, S32DS integrates Config Tools, which also allows for creating configurations similar to EB Tresos, which could make the development easier.
Please, let us know if this information was helpful or not.