Help with wiring an overhead radio to battery

I installed an overhead radio on my 2009 Pds. I ran the wires down the back hollow tube. I have an extra 12v battery. I am thinking about using it for the radio and just charging it as needed. The radio did not come with wiring instructions. I assume k just hook the red wire to the positive and black to the negative? Do I need a fuse? I'm still fairly new to this, any help
Is appreciated.