What is the Risk feature in Primavera? The risk feature is simply a risk register where you can enter details about the identified risks.
In the Risks window, you can enter name of the identified risks, their probability of occurrence, impact, activities the risks will effect. You can also enter risk action plan - a plan to do something when the risk occurs. You also can enter risk cause, effects and detailed description of the risk.
Note that the Primavera risk feature expects you to already have identified risks and associated information against each risk such as probability, impact, etc. Once you have done it, now you can use the Risk feature to enter there all the detail.
You might be wondering why the risk data doesn't effect the schedule. For example, you entered a risk with a probability of 100%. You may expect from Primavera to calculate duration reserve for that activity, labor hour reserve and also incorporate that reserve in the activity. Well, this is not possible in Primavera. However, since Oracle has another software called Primavera Risk Analysis - it is used for this purpose. You import your schedule into this software, enter all the risk data there and the software will calculate and incorporate the result of the risk into the activities.
Remember that any data you enter in the risk window will not effect the schedule in any way. It is just a record for you.