I have a question about the Yoast SEO Plug In!

On my website http://www.StreetLifeTour.com, I am trying to do some updates for for this years event. I have decided to revamp the look as well as putting a lot of effort into the SEO side of the website. I have installed the Yoast SEO Plugin. SO far, it seems intuitive and well laid out. I also like the extensions available for this plug-in. One of the first things I decided to do was to complete the Sitemap. I have tried to generate the sitemap through Yoast, and it brings me to a “404 Error not found”. So instead of doing it through Yoast I was advised I should just use “www.streetlifetour.com/Sitemap.XML” and again I get a 404 error from the Google Webmasters Dashboard. Can someone recommend me what I need to do? Thanks!