How can I add fuel to my engines that ranout of fuel? like. Engine 1 and 4 are empty and 2 and 3 are still going with a lot! How do i put some of 2 and 3's fuel to 1 and 4 engines? PMDG 747 btw

Pull up the fuel display on the EICAS and change the Xfeed and pump valves on the overhead until you get the configuration you want. Then read the Aircraft Systems manual, starting on page 44, for a detailed discussion of the fuel system

thank you!!

You did it wrong (I think). You should run from center tank, then bigger wing tanks, until all 4 wing tanks have same amount of fuel, and only then you couple them in tank-to-engine config.

If you set it up right, you don't have to do anything. You will get a warning when the center tank is emptied but it is only warning you that the switchs don't agree with the pumps because they were turned off automatically.