This is the critical section. Installing an EPLAN library is not a simple "double-click." You must use the EPLAN Parts Management interface.
If a specific library isn't on the Data Portal, many manufacturers provide .edz files or macro collections on their own support pages. eplan library download install
If you have installed a library but cannot see the macros in the symbol library picker, you likely have a path issue. This is the critical section
Click or simply close and reopen the management window to refresh the list. eplan library download install