You can download the FINAL FANTASY XIV: A Realm Reborn game client from the following link. 
Officially Download(Approximately 109MB)
This software can be used for Beta Test phase 4 (Final Beta), early access, and the official release once the game has launched.

Installation Procedure

1. Installation Setup 
To launch the installer, double click ffxivsetup.exe. 

2. Region/Language Selection 
After launching the installer, the region/language selection screen will be displayed. Select your preferred language for the installer and the game. This option will be set to your Windows region/language by default.
A User Account Control prompt may be displayed for Windows Vista® and Windows® 7 users. Select "Yes" to proceed with the installation.
Please launch the installer as a user with administrator rights. Windows Vista® and Windows® 7 users may be prompted for an administrator password.
Selecting a language different from the one set for your OS may cause the installer to display corrupted text.

3. Note on Background Applications 
Please read and follow the on-screen instructions regarding background applications and anti-virus software. Click "Next" when you are ready to continue. 

4. Select the destination folder to which the game data will be installed. To install to a different folder, click "Browse" and designate a new destination folder.
The drive selected for installation must have at least 20 GB of free space available.
The drive containing the My Documents folder must have at least 2 GB of free space available.
The drive in which Windows is installed must have at least 1 GB of free space available.
The destination folder name must not contain any double-byte characters. You now have the chance to review your settings. If you are satisfied with the settings, click "Next" to begin copying files.

5. Check the box if you wish to create a shortcut on your desktop, then click "Finish" to complete the installation.
For instructions on how to log in and start the game, please refer to the community site, "The Lodestone," which will become available at a later date.
Windows® 7 Users
If an error requesting that you install Windows Vista Service Pack 2 occurs during installation, please follow these steps:
1. Right-click ffxivsetup.exe and open "Properties." 
2. In the "Compatibility" tab, click "Change settings for all users." 
3. Uncheck the box for "Run this program in compatibility mode for:" and click "Apply."