Do not proceed if you see only one file. You need at least 2 pairs (HEX+IDX+LIB per IC).
I cannot provide a direct download link because files change, but a working example as of recent years is hosted at: Ht12e And Ht12d Proteus Library File Download
Close any active Proteus windows and restart the software to refresh the component database. Alternative: Using Built-in Equivalents Do not proceed if you see only one file