I would hook up the power wire to either the accessory terminal of the ignition switch or the input side of the ballast resistor (which should be connected to the run terminal of the ignition switch).
If you were to connect it to the fuse junction box, it would be powered all the time and the wipers wouldn't stop when you turned off the ignition. But if you have a 3 wire wiper motor, one of the wires should be connected to the fuse junction box so that the park feature works. It needs power all the time to move the wiper to park position when switched off.
I can't advise what size fuse you should use. It would depend on the amp draw of the wiper motor, but would likely be 10A or less.


Kevin
1951 Chevy 3100 work truck
Follow this saga in Project Journal
Photos
1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.