welcome to the KNIME community.
The example page is a little bit outdated and does not really show the first steps you would need to take to get the Dictionary Tagger node running. The example uses a Table Reader node which already provides preprocessed Documents. A document is a specific data type in KNIME that is used for working with nodes of the Textprocessing Extension. So, all you need to do is to convert you texts into documents by using the Strings To Document.