Imports the key specified by UserId to the current keyring.
If the FileName specifies a key file which contains multiple keys only the key belonging to UserId will be imported.
If UserId is set to "*" or "" (empty string) all keys in the key file will be imported. The ImportAllKeys setting controls the behavior of the component in this case.
Note: If you simply wish to select a key in the current ring set UserId instead.