How do I add top sites to. My iPad

If you are using Safari and want to add a bookmark to a site first navigate to the site. Then tap the Share icon. That's the square with vertical arrow. Then tap bookmark and name the new bookmark. If you have folders of bookmarks you can select which folder of bookmarks you want the new one listed under.

Ralph9430 gave an excellent response.

But if you're looking for a "Top Sites" capability similar to the one in the Mac's Safari, that does not exist on the iPad.