As a participant in the “ARRL Logbook of the World” program (see http://www.arrl.org/quick-start), your own LoTW certificate must be imported into the operating system before it can be used to authenticate against this website. The import process is described here:
- Windows
- macOS
- Ubuntu
Then follow the link “Login ARRL LoTW” and select the certificate. The query looks different depending on the selected web browser: