You are running the most recent versions of macOS and Safari
You already have Silverlight installed
It is not advised that you use Safari for Windows, as the browser has not been updated in five years.
In recent releases of macOS, as a security and energy-saving measure, Apple has disabled plug-ins by default. In order to use plug-ins like Silverlight in Safari, you need to enable them.
To enable plug-ins, first you'll want to make sure that you open Safari and navigate to the OA LodgeMaster website. You won't need to do anything on it, but you will need to leave it open. We'll get to why in a moment. Next, follow the Safari Menu to preferences. You can also use Command-comma to reach the same screen. A new window will appear with a variety of settings. This is Safari's preferences pane.
Along the top of the preferences pane are different categories. You'll want to switch to the Security category. You should be presented with a screen similar to the one to the left.
Make sure the box is checked next to "Allow Plug-ins" and click on "Plug-in Settings." A new window will open.
This new window lists all plug-ins you may have installed on your computer. Depending on the number, you will need to scroll all the way down on the left-hand menu pane to see the Silverlight plug-in.
Once you see Silverlight, you'll need to make sure that the box next to Silverlight is checked. This box allows Silverlight to run in Safari.
The next step is to configure Silverlight on the LodgeMaster website. Make sure Silverlight is selected in the left-hand pane and find the LodgeMaster website in the "Currently Open Websites" section in the main window. Click to open the drop-down, and select "On." This will enable Silverlight on the OA LodgeMaster website. To save the changes, click "Done" at the bottom of the window. This will close the window.
You are now free to close the preferences pane and resume using OA LodgeMaster as normal.