When you were using imToken 1.0, one mnemonic can only manage one Ethereum wallet. And when you use imToken 2.0, you can manage a Bitcoin wallet, an Ethereum wallet, an EOS wallet and a COSMOS wallet together with one mnemonic under a digital identity.
Case 1: If you are using imToken 2.0 for the first time, and have not backed up the mnemonic before.
You can create a new digital identity by clicking "Create Identity"
Case 2: Using imToken 2.0 for the first time, but have the mnemonic backed up from 1.0 version.
If you have previously backed up your mnemonic, you can create a digital identity by clicking "Recover Identity". The previous mnemonic can only manage one Ethereum wallet in 1.0 version. Now, this mnemonic can manage Bitcoin, Ethereum and EOS together in 2.0.