The New Project wizard is brought up by the File-New-Project... operation. This helps organize the start of a new "project" (RATS program).
The Title, Author(s) and Description fields are all optional and create comment fields at the top of the file. Note that you can always edit these later.
The Data Sources box has several choices. The most commonly used one will be the one showing in the sample ("Single Data File (not RATS format)"). This is for programs that are based upon a single text data file or Excel file or something like that. This will bring up the Data Wizard: Other Formats. Note that importing a data file can be very simple or can be fairly complicated, depending upon how well-formatted the information is. If you use "Single RATS Format File", the project dialog will bring up the Data Wizard: RATS Format Files dialog. Because those can be very large databases, you need to open the RATS format file first (File-Open operation, choose the .RAT file type to pick a RATS format data file) and choose the series that you want before doing the New Project.