Bluetooth keyboard and mouse

I've just got a new Raspi,4 from Lablists. I got a Bluetooth keyboard and mouse for it, but getting it to recognise them is another matter. I connected phone to pc some time back, and at least they divulged a serial number each. No such luck with the keyboard and mouse. They seem to be very shy altogether. Given that I can't adjust the keyboard or mouse, there's going to be issues if they are not somewhat forthcoming

Is there a recognised way of setting such things up?