Where can I download wallet?
a) You can simply use your Ethereum keystore file (generate with https://www.myetherwallet.com/ if you don't have it already) because Amabig keys are fully compatible with Ethereum keys. Later you will be able to import your Ethereum key into Amabig Wallet.
b) Or you can download and compile https://github.com/Amabig/go-amabig official client and generate your keystore file there.
We will launch Amabig Wallet soon, but for now the easiest way is to simply use your Ethereum wallet as it's 100% compatible format with Amabig wallet.