10 rounds is pretty easy. If you're playing for the first time you have to register at least one word for the round to count. You can't just let the game sit inactive and complete rounds.
You'll need to eventually play 100 rounds to earn the following:
Also if you have this achievement already form playing other version, this should pop after you play one game in the web version.
Edit: If you're not able to unlock this, keep in mind this is in beta and only open to US accounts. If your Live account is in another country you will likely not be able to unlock these achievements at this time.