In order to send messages to people who are not in your contacts list, and send unlimited friend requests, you need to upgrade to a Pro account. Without a Pro account, the limit of friend requests is 5 per day.
After upgrading your account, you will be able to send messages to any body, and it will look like this:
Conversation then automatically opens in your "Active Chats":
Get a Pro account and start chatting with any body for only $2.95 per month.
