If you are reading this page, you should have already deployed this plugin in the dropins folder.
Now, to add saerchable custom documentation to the CICS Explorer, just copy any xhtml and text files in the "mydocs" directory.
Then clicking on the menu "Help|Re-create index" will restart the workbench and a new help index for searching the documentation will be created. This new index will include any docs that have been added under "mydocs".