A change request form is a document that describes the proposed change, the reason for the change, the impact of the change, and the approval process for the change. A change request form is required for any planned changes to the network, such as adding a new network printer, to ensure that the change is authorized, documented, and communicated to all stakeholders. Submitting a change request form should happen immediately before network use is authorized, as stated in the Official CompTIA A+ Core 2 Study Guide.
The other options are either too late (documenting the date and time of the change) or too early (determining the risk level of the change and requesting an unused IP address) in the change management process.