I usually use the quick reply box. Just below it you can click "Full Reply Form" if you want to do some special editing or add smilies without typing in the code.
To answer your question about Serenia and Haven, you can do the ages in any order, but things you learn in one may be helpful to complete another. Since you're there, do as much as you can in Serenia, then go to Haven.
By the way, congratulations on finishing the chair puzzle in Spire on your own!