To play in this event you will need to download the map ( Immersed.rfa ) and add it to your BF1942 Installation.
Clicking on the link provided will initiate a map download. Once the download has completed Cut or Copy the file Immersed.rfa from your downloads folder and paste it into the Levels Directory located here -> C:\Program Files (x86)\EA Games\Battlefield 1942\Mods\bf1942\Archives\bf1942\levels