When you add your file to the Google Search console, there is an option to download an HTML verification file. Download this file to your computer. This file now needs to be uploaded to your root folder of the server. It will not affect your server, it is just needed for verification. Make sure you upload it to a main folder, and not a subfolder. Once it is uploaded, go to the address of the file, and make sure that it confirms that the file was uploaded. After this, you should press verify in the original prompt that gave you the html file. This will complete the process, and Google will search for the file in the server. It may take up to an hour to verify, but after that, you are good to go.