How to use this 12-bit ADC chip
Well, the function of the other pins is explained from page 15 of the datasheets, they are mostly used for adapting the converter to various kind of buses. Choose  the one you like better and program the FPGA accordingly, in the following pages there are diagrams for the supported bus cycles.
As an aside: you noticed that this is a 5V part, right? there aren't many FPGAs around which handle these, you'll probably need level shifters.