If you have previously lost access to your MetaMask account or simply want to import another Ethereum account to your MetaMask, this can be done by using the “IMPORT” feature within MetaMask. You will be presented a screen like the following. It is important that you have your private key or access to your private key as this will be required to import an account.
Simply insert your private key in the field provided and click on “IMPORT”. Your Ethereum wallet will be imported and you will have access to it via the upper left hand menu within MetaMask.
Additionally you can also “RESTORE” a lost cryptocurrency wallet this way as well. Restoring a wallet with MetaMask can be done via a seed phrase or private key.