You should have got the tool in the plastic wallet when you got the bike. It looks like this:-
The slot allows you slip the part around the fuel pipe and when you push the tool up towards the tank it compresses a couple of lugs which allows the fuel connection to be disengaged.
You can remove the tank without the tool by compressing the two plastic parts on either side of the coupling that releases the fuel pipe but you need to be very careful that you don't break them or the coupling as this is an integral part of the fuel pump which will need to be replaced if you screw it up.
Oh, there should be another tool in that plastic wallet that is shaped like a 'T', this is to 'bung' up the hole (if you pardon the expression) which will stop the fuel pishing out of the tank after you have disconnected the fuel coupling.