Help please

Good afternoon, good when I click on some store that is in the list of stores, the following message appears “Oops! This page was not found.
Looks like nothing was found at that location. How about trying one of the links below or doing a search?”. And I have a doubt related to the plugin, well my store the products that are made available by me are all free freight, but that of my suppliers do not, how can I at the time they are to place an order for a product made available by them, does not leave available the free shipping, and leave only the option that the seller makes available (and how can the seller make available?). It would have some tutorial attached where it shows a written tutorial, with all the features, and features that vendors can have access to.

The page I need help with: [log in to see the link]