the easiest way to get to the battery strap nut is to remove the ignition module cover then you will have easy acess to the nut on the end of the battery strap
once you remove the nut and lift that end of the strap you can then ease out the front fitting its hook shaped and fits in a slot on the front of the battery tray
once the strap is off you will find that the top cover just lifts off, if there is a full battery cover the lower part can then be eased off (can be a bit tight)
youll find at that stage that the cables are a bit shorter than youd like them to be for acess to undo the bolts (esier if the seat is removed)
this is best done with assistance as another pair of hands to hold the battery half out of the tray while you try to undo the cable bolts prevents a lot of bad language
Brian