Mattsubaru12345678909

I think my boy hooked the battery up backwards in a 2003 Subaru Outback I'm getting nothing from the ignition I can take the positive terminal and hit the solenoid and turn the key at the same time with two people and start the vehicle but I don't think the alternator is charging either I've checked all the fuses I heard something about a wire with an inline fuse a small wire by the battery or by bee fuse box under the hood but I don't know where to go from here can somebody please help me thank you and God bless Thanks