1. You just follow the step-by-step method to click the "Download" button and wait a few seconds until you can reach the page "Download" and install the .Apk file.
2. There is link in page on how to download the kingroot application v4.1 and v4.5 there you can read how to install and use the application.
Notice that this is a simple guide and resource application with informational purposes and it doesn't modify anything on your devices.