Turn off your Ace 2 and boot it into Download/Odin mode. Press and hold the Volume Down + Home + Power buttons simultaneously for a few seconds. When you see a warning screen, press Volume Up key to continue.
Open the Odin folder and run Odin3_v1.83.exe as administrator.
Now connect your Ace 2 to the computer using a compatible USB cable. Wait for a few seconds till the ID:COM port at Odin turns yellow to show that the device has been detected.