You can move money out of your Project in several ways:
Submitting expenses to withdraw funds.
Donating to another Project in the same fiscal host.
Giving the remaining balance to your Fiscal Host. You can access that option by visiting your Project's page, clicking on the gear icon next to your logo, and heading to the Advanced page.
Due to the design of the Open Project system, sometimes if you try to withdraw 100% of your balance, a small amount will be unintentionally left behind. This is usually caused by fees being hard to predict exactly.
If this happens, go to to your Project's page, click on the gear icon next to your logo, head to Advanced and use the Empty Balance button to transfer the remaining funds to your Fiscal Host.