No. If you have already submitted an anonymous disclosure the form would have instructed you to opt in to two-way messaging and provided a unique code to log-in to the messaging service. If you did not opt-in then you can not go back and amend this.
However, you can submit a new anonymous disclosure and choose to opt-in to two-way messaging. The Report + Support team will then be able to engage with the two-way messaging feature and answer any questions about your disclosure.