Hi Gods,
If you want to use the Zack et al., 2011 method (https://doi.org/10.1007/s00410-011-0609-4) you need to modify the original csv file from your ICP-MS before it is uploaded into Iolite.
Alternatively, you can do the 208 common Pb correction in Iolite using VizualAge by going Visualisations--> VizualAge --> 208 Common Pb correction (or something along those lines; i don't have Iolite infront of me).
I once tested both methods a got basically the same results.
Cheers