Follow the example circuit in the LCL7107 datasheet.
I investigated this very application for a friend who is building a power supply, and decided that the ICL7107/7106 circuit was just too much work, so we did this:
Hey DickCappels
Do you happen to know any Voltmeter based on PIC's.
I been wanting to make one for my supply.
I already have the 7107's but it does not give 2 decimal read outs.
The one you suggested is perfect but I donno atmel yet.