Secure testing is an application that allows instructor to give tests remotely while being able to make the students only have the test site open.
First you will come to the instructions page (Shown below). In the middle is a link to either the Windows version or the Macintosh Version. Click on the link that conforms to your computers operating system.
Once you click on a link, depending on the settings of your browser, it may download immediately, or might bring up a windows asking you where you want the file to be saved. Once you've decided and the file is downloaded run the file to initiate the installation of the application (shown below on mac)
On mac the file downloaded will be a zip file. When opened it should bring up a different file named something like 'Install Platinum Secure Testing.pkg'. Now double click this file to install.
If you get the prompt shown below click 'continue'
Follow prompts with 'continue', 'next' then 'install'
It may ask for your computer's administrator password to complete installation.
Once you get the screen below of successful installation then go back to your test instructions page and click 'begin test' at the very bottom.
If you know you've installed correctly but something goes wrong when you click 'begin test' try this checklist in the article here.