Your Wallet ID can be viewed by going to Settings > General.
A Wallet ID (also called your Wallet Identifier) acts similarly to a username you'd use to access your email, or log into Facebook. To log into your wallet, you'd use your Wallet ID, password, plus any form of Two Factor Authentication you've enabled.
It looks like a string of letters and numbers, like the sample Wallet ID below:
A Wallet ID is only used for the login process, and it's different from a receiving address. In other words, it can't be used to send or receive funds. Do not send funds to your wallet ID. For security reasons, we strongly recommend you don't share your Wallet ID publicly, or with anyone.