Here are some good links to various (good) products that you will need in order to use and install The Secretary (and any other CMS, and to do anything on the Web, for that matter).
An FTP program lets you upload files to your website.
Transmit
The best FTP program for the Mac. Costs only $30USD and is worth every penny.
Cyberduck
One of the best free solutions for the Mac.
FileZilla
Another good program, with versions for Mac, Windows and Linux.
A text editor is what you use to edit text files. The following programs are tailored to coding and have more advanced features than the regular text editor.
TextMate
The absolute best text editor ever made. Costs €48.75 and is totally worth it.
TextWrangler
A very solid text editor, considering it is free.
Adobe Dreamweaver
Both a text editor and a drag-and-drop visual website editor. Probably the most widely used program for this type of thing.
E-TextEditor
The Windows version of TextMate.