In any file, in the FILE menu, go to LIBRARIES & OBJECTS / MANAGE BIMCLOUD BIM SERVER LIBRARIES. In the middle of the dialog box, there is a button called UPLOAD... this brings up a typical FILE NAVIGATION box where you can navigate to the REAL LIBRARY you want to add...
HOWEVER... since you're looking for an ARCHICAD library... Graphisoft intended you to now load the AC 19 Library and the AC 19 MIGRATION LIBRARY. This last library holds all the parts from past AC Libraries that don't existing in the 19 library.
The concept is that libraries must be UPLOADED to EACH BIM SERVER (17,18, 19, etc)... Just because something was in the 17 Bim Libraries doesn't mean it will show in 19.
Let me now if this helps.
Duane
Visual Frontiers
AC25 :|: AC26 :|: AC27
:|: Enscape3.4:|:TwinMotion
DellXPS 4.7ghz i7:|: 8gb GPU 1070ti / Alienware M18 Laptop