Download the .mcworld file and after it downloads at your device, click on it. Wait for inport status in-game, and the map will be avaliable to play.
If you're playing at Minecraft for Windows, open the game and press Import world at the world selector, select the .mcworld file and wait until it finishes importing in-game.
Once you click the .mcworld file, Minecraft will open automatically. If your device says it doesn't have any app compatible with that file type or it doesn't allow you to access the Android folder, you must connect your device via USB to a PC and import it manually.
The "Import world" feature is only available at Minecraft for Windows client, we've verified and Android client hasn't this version. We doesn't know if Minecraft for iOS has this feature.
.zip (Windows):
Download the file and unzip it as a folder.
Press Windows + R, and write: %appdata% (as shown in the photo).
Then, search for a folder named "Minecraft Bedrock".
Once in the folder, go to the folder named "Users".
Then, you'll find 3 folders: two of them have a really long number and the remaining one names "Shared".
Click on the folders with the numbers and open "games" and then "com.mojang" until you find a folder named "minecraftWorlds". (If you don't find the folder named "minecraftWorlds" in the first/second folder, try to search at the other one).
Open it and cut/copy and paste the unzipped world folder to "minecraftWorlds".
Finally, open Minecraft, find your world and the map will be avaliable to play!
.zip (Android):
Extract the ZIP file, and move the unzipped folder to one of these two locations: