On the policy properties page you can configure the Enforcement Readiness Period (i.e. Staging) and Signature Staging.
Any new policy items, e.g. new file types, will be determined by the Enforcement Readiness Period, if you select Perform Staging on the new object when adding it.
In regards Signature Staging, this is just for new Attack Signatures. By default this is enabled. This means when you update your signatures the new ones will be in staging and (optionally) the updated ones too. There is a seperate tick box for Updated Signatures.