Hi Axel.

Check out the margin rates page here. In France it should be Euro, right?

https://www.interactivebrokers.com/en/trading/margin-rates.php

To setup for margin, you'll want to link IBKR to a bank account, and set up some form of two factor authentication. I use the IBKR mobile app for 2FA and have IBKR linked to my normal bank account via ACH.

To initiate a margin withdraw from IBKR, click "Withdraw", then select the account you just setup, and on the next screen you should see "Cash Available for Withdrawal (assuming margin loan)". You can withdraw up to the limit based on your account balance and your security device.

https://guides.interactivebrokers.com/am3/am/funding/withdrawallimits.htm

If you just opened the account, it could take up to 30 days for your shares to gradually be available for margin.

Hope this helps!