Look below your post where it says 'new attachment'.
Press 'browse' and select a picture from your drive.
Press 'add attachment'.
The file will then appear in a 'list' at the bottom of the post (well, it's a list if you add more than one attachment!)
You then select the attachment you want to insert, place your cursor where you want it to go in your message, and press 'insert into post'.
You will only see the link at first, to view the final effect press the 'preview post' button.
edit: doh! R beat me to it...
Press 'browse' and select a picture from your drive.
Press 'add attachment'.
The file will then appear in a 'list' at the bottom of the post (well, it's a list if you add more than one attachment!)
You then select the attachment you want to insert, place your cursor where you want it to go in your message, and press 'insert into post'.
You will only see the link at first, to view the final effect press the 'preview post' button.
edit: doh! R beat me to it...