To check for updates to L3DT, select the 'Help→Check for updates…' menu item. This will open the Update manager window, shown below:
When the update manager is opened, it will connect to the Bundysoft.com servers to check for any updates or alerts. If found, they will be displayed in the tree view in the top half of the window. When you select one of the available updates/alerts, a descriptive message will be provided in the lower half of the window, as well as a link to the download or to more information on the website.