It's allways nice to have lots of fuses. Let it be to many instead of to few.
You must install a fuse within 10 cm of the battery on the positive cable. Just to be at the safe side, fuse the monitor to - if it's connected to your powersupply.
Try to use the right fusesize. If your carputer measures 5 amp of usage, use a 7 or 10 amp fuse.
Another way of getting the right fuse is to try different sizes. Use a slightly bigger fuse than the largerst blown.