From man gpg
What is the OpenPGP 'settings' for the gpg path and options, for example at the 'advanced' tab?
Add file to the current list of keyrings. If file begins with a tilde and a slash, these
are replaced by the $HOME directory. If the filename does not contain a slash, it is
assumed to be in the GnuPG home directory ("~/.gnupg" if --homedir or $GNUPGHOME is not
Note that this adds a keyring to the current list. If the intent is to use the specified
keyring alone, use --keyring along with --no-default-keyring.