If you have a single channel, header-less data file, and are satisfied with your changes to the default import header parameters, then you can click on the OK button and proceed with the import. You will see status messages displayed at the bottom of the screen while the data is being imported. Once imported, the Series will be available to load via the pull-down menus: File, Open, Series.
If your data file is a multi-column or interlaced multi-channel file, has a non-DADiSP header attached, or has a separate header file, you will want to use the Advanced Button or the Load Button.
Note that not all of DADiSP's import keywords are available in the default import header. If this is the case, then you will need to create a separate ASCII file for your header. See the sections on Creating a DADiSP Header File and Using the Load Button.