Hi,
As explained in IBERT’s model card: fine-tuning the model consists of 3 stages:

full precision fine-tuning
quantization
quantization-aware training.

So for the first step, you can fine-tune IBERT just as any BERT model. You can take a look at the example scripts 1 as well as the official QA notebook 2.
Step 2 is simply setting the quantize attribute of the model’s configuration to True.
Step 3 is the same as step 1, but now with your quantized model.