I am going to try to install a 6 or 8 inch led tube under the driver side dash.I know I need an inline fuse to connect to the battery, I found an inline fuse with a 4gauge wire connected already for the battery..I need to know how many watts would I need for the fuse? I might even stick one under the drivers side. So any tips would be great.

Thanks

Your looking for voltage, not wattage. Get a 30amp inline fuse then whether you got a fat or thin tip fuse for that in-line.