Why don't you look at IPP documentation?
IPP manual, volume 1. Chapter 6 IIR Filter Functions, page 6-94
To initialize and use an IIR filter, follow this general scheme:
In IPP for some function family we provide two approaches, the first, function allocate memory internally, which not always might be what customer wants and second when you can allocate memory by your own way (might be important for example in kernel mode drivers). For the second case, we provide function which tell you how many memory you need to allocate and also function which initialise that memory block. Of course it is your responisbility to free that memory by appropriate function (CRT free() if you use malloc() or delete if you use new or whatever)