The answer to this and your answer depends on too many other factors. I take it you are looking for a step by step and that's not possible unless we use generic instructions. The answer also changed depending on the PDA.
But the damning issue here is Outlook Web Access. That is not something we sync with but point a web browser at. For that you use your PDAs web browser and hope it works.
How do you set up windows mobile to sync with my email account at work. We use outlook web access. Is it also possible to sync contacts automatically with this service and how?