Here is a video guide with English commentary for this achievement! This achievement is easily obtainable by playing a multiplayer game on Endor. In the game mode selection screen, you can choose a specific map, so make sure to choose a game type with an Endor map. Next, this can only happen if you are playing as an Imperial. Make your way to a treehouse and stand under it for a few seconds and you should get hit by an Ewok.
Here is a playlist of guides for this game!
https://www.youtube.com/playlist?list=PL-HeW6XkKdUJlEkf4FCnF...