Q: Re-connect wireless keyboard

I can not simple log-in to the computer ... I get no-where. it seems tooo bad to buy another USB-keyboard just for re-connections. please guide me to a key command to let go of this trouble. Appreciate all guidning

Thanks, however the trick ... that was not obvious is to keep/click the power button until the connection is established...This took about 2-3 minutes, a lot longer that I expected. Also the lights was a bit missleading...first fixed light..then blinking light ... and I think it stopped for a while ...then the screen awakes and show the communication square ...it is actually trying to connect. Finally it connected.