H1 tags are HTML codes that create headings on your page. If Traffic Travis gives you a page warning saying that your page has too many H1 tags, you need to visit that page and view its source code to find the problem.
To view a page's source code, just right-click somewhere on the page and then click "View page source," "View source" or the equivalent. You can also just press Ctrl+U on most browsers.
Once the tab or window containing the source code appears, search for H1 tags by clicking Edit > Find in the top menu (or pressing Ctrl+F) and then typing H1 to search for all appearances of the H1 tag.
This will show you all of the places where H1 tags appear. You'll want to remove all duplicates until only one set of H1 tags (both an <h1> and a </h1>) remains. In most cases, the H1 tags should only be used for the page's title.
Once you have identified the duplicates, go to your website's admin area. Switch your editor from WYSIWYG to HTML (from Visual to Text in WordPress) and look for the extra H1 codes that you found. Edit out the extra H1 tags, replacing them with H2 tags or other appropriate formatting, and then save/publish.
You can then update your Page Warnings in the My Site tab by selecting the page you edited and clicking the green "UPDATE" button in the lower left.