To share a video website hosted by SproutVideo, you can simply share the URL you selected when signing up, which will send people to your site's homepage. It probably looks something like this:
If you created a custom CNAME record for your video site, then you would want to share that URL instead, although either URL will work and will send viewers to the same place. It probably looks something like this:
If you are unsure of your site URL, you can use the "Go To Site" link in the Site drop down menu to open it in a new browser window or tab.
You can also share a link directly to a video, which is located in the Sharing box on the video detail page. Here is a help article that walks you through locating that link: