The menu item to tell Skyline to extract chromatograms from a .d file is:
File > Import > Results

In order to use that menu item you have to have first told Skyline which molecule(s) to look for perhaps by using the "Edit > Insert > Peptides" menu item.

The "Import Results Files" dialog allows you to browse your file system. In order to be able to select a ".d" folder in the Import Results Files dialog, that .d folder would need to contain a folder named "AcqData" and the AcqData folder would need to contain a file named "analysis.baf", "analysis.tdf", or "analysis.tsf".

If you just want to look at spectra in a .d folder, and not extract chromatograms for specific analytes, then you could use "SeeMS.exe" which gets installed when you install ProteoWizard:
https://proteowizard.sourceforge.io/download.html

-- Nick