When learning our way around this new platform, it helps to keep this in mind:
On the OLD site, we added videos and music from the video or music area or from the main page. Now we add those things from our own profile area- we go to our "Video" TAB on our profile page and click the PLUS+ button to add our own video...which is then seen in the main videos section.
Likewise, we used to go to another person's profile page and look for 'send message' button to message them. Now we send all messages from our own profile area's Private Messages area.
Content that belongs to us or that we ourselves create or add to the site are often added/controlled from our own profile page areas now.
To send a PM:
As Robin said, Hover on your top navbar NAME LINK, and the drop-dpown menu will show "Private Messages"- click to get to your Message area.
There you can see past message threads you may have sent or received. To create a NEW pm, look there top right for "New Message" button. go there and start typing a name, like John...and all members with John will show in a list as you type (autofill) and you pick which John you want to send it to. and you type your PM and then send.
Make sure you look in your "Notifications TAB" in your Account Settings area, to checkbox the things you would like to receive email notifications on...like be notified when you receive a private message, for example.
Though at first this all feels too different and unfamiliar, once we do these things a few times it starts to feel more normal...it happened to me.
Hope this helps!
Those irritated by grain of sand best avoid beach.
-Strumelia proverb c.1990