Once you've found a module you would like to test, you need to know how to add and install that module.
You will need to have your web server running with Moodle installed. If you are not an administrator of the site, you will need assistance from someone who is.
To install a module, you will need to access your file browser to copy files and a web browser to see the results. You will need to be able to unzip files as this is how files in a module are packaged together.
On the entry page for the module, look for the links at the bottom-right of the description. If you have an older version of Moodle, look for the version of the module that is suitable for your version.