You can find installation instructions release notes included in the ZIP file you downloaded. It is recommended to use "Check for updates" instead of "Install new software". Installation instructions contains step-by-step process:
1. Run KDS 3.0.0
2. Select Window > Preferences
3. Select Install/Update > Available Software Sites
4. Add a new install site using the Add... button
5. Type name of the install site into the Name field (e.g. KDS 3.1.0).
6. Click on the Archive... button and find the KDS_3.1.0.zip.
7. Confirm site addition by clicking on OK button.
8. Close Preferences windows by clicking on OK button.
9. Select Help > Check for Updates
10. Continue with the wizard. Accept the license agreement during the installation process.
11. Restart KDS.