You need to remove the air box.
Then the big rubber cover that fits snuggly over the battery.
Undo the cables attached to the posts and the hold down clamp.
Lift out the battery.
Reverse the procedure to install the new (or recharged) battery.
If you buy a battery charger that is designed for minimal use vehicles such as sleds, (Battery Tender) they come with a wiring harness that attaches to your battery permanently that has a rubber cap for the connector that you can cable tie to the frame behind the air box where it's easily accesible. Then leave the battery plugged in when she's not riding. This type of charger will give a trickle charge and once it's fully charged, reduces down to a maintenance rate of charge. This way the battery will always be at it's optimal charge.
Then she's happy again.
And when she's happy, everybody is happy.