The fuse kit goes on the Positive Cable between your Power Inverter and Battery. This is done closer to the battery where the source of the short will likely occur. Placing the fuse within a foot of the battery is typical of the most applications.
The lugs on the end of your inverter cables, will seat on the stud of one end of the fuse holder. The ANL fuse will sit either above or below this lug. Placement doesn't matter. You will do the same using a short jumper cable. Do not connect to the battery until fuse and cables are securely fastened. Using the supplied nut and washer, you will secure the fuse and the cables on both sides of the fuse holder. Place the cover over the fuse to prevent a ground short and then proceed to connect the inverter as you would normally, using the open end of the jumper cable.