First and foremost, you must have purchased DCS: Normandy 1944 Map, It is required for DCS World 2 Open Alpha
You can buy it in our E-Shop: DCS: Normandy 1944 Map
Once you have DCS World 2 openalpha installed, login to the module manager in game, your purchased terrain should be available for download.
If not please check your purchase is bound to your ED account here using the license check.
If you still cannot install Normandy map and Assets pack