To send a message to another PPS user click Messages from the main menu.
From here, choose the recipient, type a subject and the message detail and click Send Message.
In this window you can also view any received messages and review sent messages via the Inbox and Outbox tabs.
Any new messages will be marked with a red "New" label.
When viewing sent and received messages you can filter by recipient or sender by using the drop down menu in the relevant tab.