Pairing wireless mouse and keyboard

Just bought a 2015 iMac and cannot get the keyboard or mouse paired. Both turn on, the keyboard flashes 2x blinking indicating it is discoverable - but I can’t do anything because the mouse is frozen in the upper corner and nothing I touch on the keyboard or mouse will move it! HELP please, I don’t see how I can move the arrow til the mouse works! Thanks

ps it was a work computer so it was wiped entirely clean and the Welcome box is up but again I can do nothing without a responsive mouse or keyboard