How do I change the main fuse in a 1991 Mazda 323?

jumper cables/terminals mismatched during a jump, pretty sure i just need to replace the main fuse. what tools do i need and instructions, please?How do I change the main fuse in a 1991 Mazda 323?
It is under the hood, inside the fuse box on the right side I believe. It is the 80 amp one.

Instructions say to disconnect the negative pole and that there are two bolts retaining it. if so they are either a 6, or 8 mm. I don't think they could be any bigger.

cat

Will giving my 6 week old