The daytrade session for most futures instruments is 5:00 PM until 3:45 PM the next day, Central time; so, you can hold a position during the overnight hours (US time) without an additional margin requirement.
If you want to hold a position past the close of the trading session, you must have sufficient net liquidating value above the Initial Margin requirement.
Please refer to Tradovate's Margin Page for specific margin requirements.
You can monitor your margin usage in the platform with a general overview on the dashboard:
and can get a detailed view in the Account Reports.