The FLink tool has been retired. Please consider using the Entrez Utility (EUtilties) to create your own scripting solution https://www.ncbi.nlm.nih.gov/books/NBK25501.
FAQs are answered here. The "How To" page offers quick start guides for some common types of searches,and the FLink Help document provides detailed descriptions of the input required, output displays, and the program's features and functions.