Unzip it. You will find 3 files (EREntityToHTML-x.x.x.jar, index.css and entity.css) inside.
Drag the downloaded .jar file to an open instance of Astah. A pop-up will appear asking you to confirm installation choose [Yes]. Restart Astah.
If you see the [Px3Tool] option under [Tools], that means the installation has completed successfully!
How to Use
Open the file that contains the ER Models you want to export to HTML.
Go to [Tools] – [Px3Tool] – [EREntityToHTML].
A pop-up will appear when the HTML export completes.
Save both index.css and entity.css files to the folder where index.html was saved to apply style sheets.
Samples
Exporting the ER Model above (this diagram can be found in sample.asta included in Astah Installation folder) results in the lists below. Entity list on the left and the Customer Entity on the right.