From the main page of MetaMask, you can choose the option to import or create a new wallet. Please note that the password you create to access your MetaMask wallet is secured on your device and not on any servers of MetaMask Extension. So, when you are provided with the wallet's SRP please consider it to be the master key of the wallet and do not lose it under any circumstances. This SRP or the Secret Recovery Phrase of MetaMask also comes into action in case you install the MetaMask extension on another device or browser. In case you ever forget your password, just use this Seed Phrase to retrieve your wallet. The same goes for those users who are using MetaMask on their mobile devices.