Use the word copyright and/or the © symbol. Put the copyright holder's name and year of copyright, then add any additional info you want. Look at any piece of published music for examples.

Use Finale's text tool to add this info. to the bottom of page 1.

And use a Text block. Text menu -> Inserts -> Copyright text (as defined in ScoreManager -> File Info) and Copyright Symbol.

Proper wording is almost anything. Just copy it from another score. (No, the copyright notice is not copyrighted.)

On a Mac, the © symbol is made by holding the option key while you type g. 

>Use the word copyright and/or the © symbol.< plus the year.

Since 1989, the Copyright notice is optional. It is still recommended, however, for one reason: A copyright infringer cannot claim innocent infringement as a partial defense to mitigate damages if the infringer had access to a copy of the work that bore a copyright notice