New Magic Keyboard won't connect to IMac

I just purchased a new Magic Keyboard to replace the last one that was damaged. I cannot get it to connect to my IMac to go wireless and the sound does not work, I get the F key functions instead. The Bluetooth is turned on and I have removed the previous keyboard. I am fairly computer literate but this has be stumped. Any help with this problem would be greatly appreciated. Thank you

Catherine Smith aka doccat5