Help needed : How to use internal PLL of AD9858

As you may know, AD9858 is a DDS produced by Analog Devices. It can be used as a frequency divider, mixer and also a PLL. In order to use it as a frequency divider, a clock reference is needed. Consider the case that you are going to generate 100 MHz frequency with the clock of 1 GHz. It is possible that you give it an externally generated clock. But is also gives you the possibility to use its internal PLL and generate 1 GHz with its own PLL. Here only a 10 MHz clock for example is needed which can be generated more simply than 1 GHz.
I would be thankful if any expert in this regard can give me a help how I can run its internal PLL.
Thanks