Withdrawing funds from zkSync differs depending on the type of wallet you have.
Withdraw funds from a regular account
If your address is a regular externally owned account; you should visit zkSync's Wallet page and withdraw them in the browser.
Withdraw funds from a smart contract account
If your contract can execute arbitrary transactions, you can email Matter Labs ([email protected]) or hop in the zkSync Discord to ask about the best way to connect it to zkSync (assuming you can't connect it from https://wallet.zksync.io/)
Alternatively, if you just want to withdraw funds to L1, you can use the zkSync force exit npm package. This will let any account force push funds from zkSync to L1 if the address has never interacted with zkSync.
You can do this with:
npm install -g zksync-force-exit-cli
zksync-force-exit -k <privateKeyOfAddressToSendTxFrom> -a