By now you probably need a new set of batteries too.....in addition to whatever the original problem is/was.
You should NOT let them sit in a discharged or unknown state over a long period of time like that.
Let's hope that there is also a bad connection at the negative battery post or an intermediate cable. None of that explains the blown fuse though.
At the very least you will need an external battery charger to get them back up to a known condition.
Then you need a multi-meter and some time.......or a professional vehicle electrics mechanic.