have you actually looked at the datasheet? it gives you a nice little hint as to where to look. (i.e., it points to an application note titled: “Building a Battery-Operated Auto Ranging DVM with the ICL7106”.) the 7106 and 7107 are very similar parts.
In general, your first stop on a journey like this should be at the datasheet for the part.
I suggest that you divide and conquer. Let's take a paragraph from the datasheet. You read the paragraph and tell us if you understand it or not. If you do then go on to the next paragraph. If you don't, reproduce the paragraph or give us a link and we'll help explain what is going on. I suspect there are other participants who will also be interested in this.
range in my schematic is controled by one resistor (R3). I just need easy circuit which can switch right resistor in right time:
0 - 2 V ............ R3 = 0 ohm 1%
0 - 20 V ........... R3 = 1.2 Kohm 1%
0 - 200 V .......... R3 = 12 Kohm 1%
0 - 2000 V ......... R3 = 120 Kohm 1%