Here is the direct link to download Workflow Manager Client
The download location for Workflow Manager Client is less than obvious. This little blog post is to hopefully make it easier to "Goggle" for.
To download manually:
1) Go to Microsoft Download Center - Workflow Manager 1.0
2) Click the big orange download button.
3) Choose (check) "WorkflowClient.exe" from the list and click next.
After Installing you will need need to restart the server.
You also might need to open up the firewall ports (12290/12291) on your Workflow Manager server. (Assuming you have installed the client for the purpose of connecting a new computer to the Workflow Manager.)