Cash is always deposited into your Coinbase Inc. (CBI) spot account. Cash will automatically be transferred to your Coinbase Financial Markets (CFM) futures account to satisfy margin requirements.
You can add cash either from the bank account linked to your Coinbase Inc. spot account or from your USD balance. This can be done either through a web browser or the Coinbase mobile app.
Learn how to link a bank account.
Are there any additional fees I should be aware of?
If your liquidation buffer hits 0%, CFM will start liquidating your positions and standard transaction fees apply. You can review your futures agreements and disclosures here.