This dialog is used to select a pin network part. These would normally be 2 pin parts.
Locating this option
Available from: Setup menu > Technology option > Pin Network tab > Add or Edit button
Using this option
To select a part, you can select a library from the list of available libraries or choose All Libraries. All suitable (2 pin) parts in the selected library are listed. Simply select a part from the list and press OK.
Alternatively, you can type the name of a part directly into the bottom edit box. If you type the part name, it is not guaranteed to exist in any library, but would obviously need to be created before the Pin Network is used.