General Maintenance & Repairs - Hard Wiring Cooling Fan

I've got an aftermarket single fan on the car that was there when I picked it up. I've now found out that it isn't working with the stock wiring the way they had it set up. I know the fan works, tested the two leads with a battery, and I just want to wire it directly to switch off the battery.

Is it that simple? Positive fan wire to switch, switch to positive terminal, negative fan wire to ground or negative terminal?

Also, what size wire? 14 gauge? Fuse necessary?

I don't want to burn up the wiring or the fan motor so any advice from anyone would be great.

Thanks