When you click on their profile, up on the right you should see a green button option to "Follow Them" - you can't PM someone unless you're following them. If you area following them, you'll see two options there, both grey - "Send PM" and "Unfollow".
When you click on their profile, up on the right you should see a green button option to "Follow Them" - you can't PM someone unless you're following them. If you area following them, you'll see two options there, both grey - "Send PM" and "Unfollow".
Edit: See point 6 on the FAQ: Your Account.