Open/load the map you wish to be an WP map/world.
Go to the “Tools” menu, look towards the bottom, find the World Partition section, and choose “Convert Level”, Now select the map you wish to enable WP for.
Next, LEAVE the convert in place option to EMPTY or NO, if you choose yes you’ll likely get a failed conversion and possibly even a crash window.
Convert with all default options selected, and you “should” get a successful message.
Now open your newly converted WP map.
To clarify, if you don’t already have a map that you want to be WP, create one first.
If you have one you want to convert, then open that map and follow the above.
Note: You don’t have to “enable” WP in settings now like it was in EA