Windows

You can get the Windows client here.

To install the client directly from your browser...
1 - Click the client link above and select the option to run the program.
2 - Follow the Setup instructions.

To download and install the client later...
1 - Click the link above and select the option to save the file.
2 - Find a memorable spot to save the installation file (maybe your desktop).
3 - Once the file has been downloaded, you can run it at any time by finding it and double-clicking the file.
4 - Follow the Setup instructions.

Macintosh

You can get the client for OSX here.
You can get the client for OS9 here.

To install the client...
1 - Click the link above to download the installation archive to your system.
2 - Decompress the downloaded install file using an appropriate utility.
(If your browser doesn't support decompression automatically, decompress the downloaded install file using Stuffit Expander or a similar application.)
3 - Open the Citrix ICA Client folder created by the decompression utility.
4 - Double click the Installer icon to run the installation program.
5 - Follow the setup instructions. Please leave the settings at their defaults.

Configuring Internet Explorer
1 - From the MetaFrame Applications for Macintosh page, select one of the application links.
2 - You will receive an Unhandled File Type error message. Press the Application button.
3 - At the Open screen, select the Citrix ICA Client folder from your Hard Drive (this is the default installation location for the Citrix client)
4 - Select the Citrix ICA Client Loader and press Open. Your selected application should start up at this time.

Citrix

Some users have better luck getting their client from the Citrix website.
Select "Download" from the top of the page.
Select "Clients" from either the middle section or the right-hand menu.
Pick the appropriate "Citrix Presentation Server" client for your operating system.