now then i wish to add a rev counter.....before you all say serach i have...but i;m an idiot and couldn't understand half of it

anywho. i got a rev counter from a regular 3 clock dash which i hope to be getting the pod for later on. i want to use my original 2 clocks the speedo and the fuel/temp gauges. then add the rev counter on by itself. but i don't have the foggiest idea how to wire it up,

theres the back of the rev counter. the current dial i have are the two clock ones and its a 1982 Austin Mini. i need a proper idiots guide to adding a rev counter in. were to get power feed from for the rev counter. do i need any fuses or anything. gauge of wire i want to use.
also. on the rev counter there are two big square holes. i reccon their for light as there are no lights in the counter. so i also need to know were to get some lights and how to add them in.....i say lights. i know theres a backlight but theres one at the bottom....what on earths that for?
sorry for asking so many questions but i really have no clue what to do.
Please help me. if you would be so kind.
Cheers