You may rename it, but be sure to keep the .html or .htm extension
Open the file in Internet Explorer
Try creating a new tiddler using the new tiddler button in the sidebar. Type some content for the tiddler, and click the ok button
Save your changes by clicking the save changes button in the sidebar. Internet Explorer will ask for your consent to save the file locally by presenting a file Save As dialog.
Refresh the browser window to verify that your changes have been saved correctly