In order to make the factory library available in the KONTAKT database, the factory library folder must be in the folder list on the Database tab in the main options of KONTAKT. Per default the factory library path is added to the database path(s) automatically, when you install KONTAKT 5 with the library component selected. However, if you install KONTAKT 5 or KOMPLETE 8 without the library component (e.g. since you already have the library on an external hard disk), then you need to manually add your KONTAKT 5 library path on the option's Database tab and press the Update button thereafter to import the factory library in the database.
Add the Kontakt 5 Library folder on the Database tab and press Update