I'm refraining from opening the packet with the instructions in until I've got it home and checked it's the same size as my current battery
I really should stop reading stuff on the internet...now I've read that the first charge must be a trickle charge, not a full power charge

I just usually connect my charger, select 'motorbike' (rather than car, boat, etc.) and leave it to charge up.
And is it meant to be done outside? It's not really an option to leave it outside all night in this weather...