I'l go for the explanation.
A lamp circuit is the most basic electrical circuit I can think of.
power from battery, to lamp switch, thru fuse, to lamp. one side of lamp is grounded.
find the wire that feeds the ignition switch.. hook the feed wire for the lmaps up to the terminal that wire that feeds the ignition is connected to.. now both are connected there.. use a lamp switch with a fuse. run wire from the lamp switch terminals to your lamps.. ground the lamps to a good ground.. 50 yr old rusty sheet metal may not do it.. so I like to run a ground wire from under the lamp to a good spot on the cast iron frame somewhere.
awg 14 wire is usually fine for lamps.