alaram will not silance

Hi Guys, I have a 1991 750il, I left the lights on yesterday. So I took the battery out and recharged it. When I tried to hook up the battery up again, the alarm keeps sounding. I have tried all the obvious stuff. Like hit the off button on the key when it sounds. I also tried to put the key in the ignition and start it while the alarm is sounding. What I do notice is the small red light in the center of the dash is on all the time, I didn’t notice this before?? Should it be on? Can anyone help me with this?