You're going to need a CTI Server in between the NICE server and the PBX (i.e. CenterVu, CT Connect, Geotel, Genesys or something like that that NICE supports).
See if you have either one of these options for connection to the CLS. The CLS was probably sold with a specific switch configuration, so take a look on the CLS and see if it matches any of the ones I just mentioned.