Go to https://fortmatic.com/ and click on Wallet in the navigation bar.
Click on "Export private key". You should then be able to download your private key. Make sure you keep this in a safe place. This is the key to your wallet and anyone who has this has access to it.
You can then import the private key into MetaMask by following this guide: https://metamask.zendesk.com/hc/en-us/articles/360015489331-How-to-import-an-Account