Simple Instructions:
To add metadata that has an existing value, first select the file, then select
the required value from the value tree, expanding hierarchy folders as
necessary. The value of the selected entry automatically appears in the Value
text field (alternatively, use the value tree's auto-select and auto-complete
features). Click "Append" to add the metadata to the selected file.
The process of adding metadata with already-existing values to folders
or multiple files is just the same.