Where do I install it, and how do I know I have the real one?

Install it from the Chrome Web Store, and get to that listing by following a link from a Creta site — the Wallet page inside Creta Games & Clubs links straight to it. Do not install a “Creta Wallet” from a link someone sent you, from a search advert, or as a file to load by hand.

One check settles it: the real listing's address ends in the extension id khkgonklnkgfcglcoegbmaenlkoncgjd. Every Creta site looks for the wallet by exactly that id, so anything else is not ours, no matter what it is called or which logo it uses.

Fake wallet extensions exist for one purpose — to capture the seed phrase you type into them. If you have already entered a seed phrase into something you now doubt, treat that wallet as compromised and move its contents to a new one.