Import of Excel Files is explained in the yEd Manual.
Since you need two different visual representations for your nodes, you will have to add a dedicated column to your node data which yEd can use to determine which visualization to use. The basic approach is as follows:
Structure your spreadsheet data as explained in Import of Excel Files.
Import your data with only one visualization for all nodes.
Use yEd's properties mapper to adjust the visualizations depending on the custom property corresponding to the data in the dedicated column mentioned above.