I know that lately, we've gained a lot of new members which is awesome and a lot of those new members are coming from other forums that may use vBulletin and their Private Message (PM) system. Here, we use the XenForo forum software which is (IMHO) much better than vBulletin. The "Conversation" system here is the same as the PM system on vBulletin. So if you want to PM another member, just click their username in a post, and click on "Start Conversation". To see all of your PMs, click on your profile and go to Inbox. Hope this helps.