How to attach picture to private massage

[Sophia]

Hi,
I know how to attach a picture to a post but I'm unable to do so in a private message.
Copy-paste or dragging doesn't work and I don't see a button for that, either.
When I copy paste I see the picture when writing but it doesn't appear in the sent message.

I use firefox on Linux.
Thanks

 

[Greg Bernhardt]

At this time only Gold members are allowed attachments in conversations

 

[Sophia]

At this time only Gold members are allowed attachments in conversations

Oh I see, thank you for the answer