The settings for your site’s meta data can be edited in the Settings section of your wordpress main admin section.
From this section you can add Front Page Description, Front Page Keywords, and site wide meta tags.
Additionally you can set metadata information for each individual page and post on your website right there in the editing section. When you edit an existing page/post or add a new page/post there will be a Meta Data section towards the bottom of the page that will allow you to set data that is specific to that page.
Having set the above data you can check it has been added to your sites code by visiting any page in your web browser then right clicking anywhere on the page and selecting “View Source” or “Source”. Towards the top of the page you should see the information you have set.