After the download is complete, drag the downloaded .jar file to an open instance of Astah. A pop-up will appear asking you to confirm installation. Choose [Yes], then restart Astah.
If you see [yUML] under [Tools], the installation is complete.
How to Use
Open a project file that includes the diagrams you want to convert to yUML, and go to [Tools] – [yUML] – [Convert to yUML diagrams].
The [yUML diagram viewer] opens. Click [Copy] to copy the text that represents the diagram in yUML.