Hi @Kalase,
For an external project, it will depend widely from which IDE you are trying to import, what type of project and with which MCU. You can find these two HOWTO guides on creating a makefile project from an existing one, and how to create a new application project:
You can also find the "Creating and building a project" section from the S32DS User Guide;

This document is found under the Design Studio installation path:
C:\nxp\S32DS.3.5\S32DS\help\pdf
I hope you find this helpful.
Best regards,
Julián