One has at least two options, defining a User command, or using Quick build. There is no difference between Windows and Linux (AFAIR, I'll check later), can't say about OS X.
User command
Go to User ⭢ User commands ⭢ Edit User commands.

Edit one of the free commands, give it a reasonable name, and use
arara %.tex
as the command. % is a placeholder for the filename without extension, as mentioned in the dialog:

Quick build
The Quick build is defined in Options ⭢ Configure Texmaker ⭢ Quick build. Choose User, and type the same command as above:

Use
- User commands can be accessed via the menu, or the keyboard shortcut Alt + Shift + function key, as seen in the first screenshot.
- The quick build has keyboard shortcut F1, and is also found in the Tools menu. (The shortcut can be changed in Options ⭢ Configure ⭢ Shortcuts)
There is a build button on the toolbar, and this can be configured to use anyone of the defined build tools, including user commands. Click the name of the tool to open a list of all available build tools, and click the arrow to compile.

I do not think it is possible to create a new button altogether.
arara %.tex --verbose --log |evince %.pdfin bothuser commandandQuickBuildapproaches withBuilt-in-viewerandEmbedticked. Depending on pdfviewer choice, output pdf will automatically refresh in integrated pdf viewer on each run. customizing QuickBuild User – texenthusiast Apr 10 '13 at 20:47arara --verbose %.texinstead. I'll see about editing my answer. See also texenthusiast's comment above. – Torbjørn T. Jul 19 '14 at 17:23ararathere – NobbZ Jul 20 '14 at 08:17