in my owneres manual it says i need a 15amp fuse, but i don't know how to hook it up/where/ and where to get the fuse at
buy a fuse holder from walmart or any elctronic store get a 15 amp fuse (never go over 15amp) hook it to the power wire on the HU and the to the a hot wire (Cars 12 volt charge thats on when you switch the car on) the same wire as the stock hu get so wire crimps to from walmart and get a wire crimper(tool) to crimp the wire so the will stay together
This is a stock headunit? Pull it out and locate the fuse, it's most likely easily accessible on the back of the unit(if it even exists there).
Though, more likely if it's blown, the fuse the manual is referring to is the one in the fuse block (The fuse block is the collection of all of the fuses in the car located under the left side of the steering wheel). The manual should indicate the location via a diagram/layout of the fuses.