Hi,
The information about WebStore was previously under About > Features, but it was kind of hard to find there so I just moved it under Documentation
http://www.mojoportal.com/e-commercesolution.aspx
If you mean how do I run it in Visual Studio, you use the mojoportal.sln file, rebuild the entire solution so it copies its files up to the main Web for running. Make sure and visit /Setup/Default.aspx so it installs the db scripts and configures the feature. You never run the WebStore.UI project directly, you have to always use mojoPortal.Web as the Startup Project in order to run in the VS Web server or debugger.
Then add an instance of WebStore to a page like any other feature, and configure ecommerce accoutns as indicated in the linked document.
Hope it helps,
Joe