Quote- How do I create signatures?
Go to personal settings > identities
Quote- I've tried to import my address book from Outlook but nothing works, Is there a solution?
may be if you could give more info than "nothing works" :/
Quote- Can I put the preview pane on the right hand side instead of at the bottom?
There are instructions for making a 3 col skin on the forum, a quick search should find them
Quote- Can I add extra columns to the mailbox view?
yes, click on the list options icon at the left hand end of the current column headings