After installing VirtueMart on a Joomla 2.5 site, it should occur in the Components menu in the Joomla! backend. In my case, it didn’t show up.
The problem can be caused by the Xmap – Virtuemart plugin not being enabled.
Go to the Extensions menu and then select Plug-in Manager.
In the filter box, type "xmap" and press enter.
In the list displaying, check if the Xmap – Virtuemart plugin is disabled (status icon is red).
Then click the status icon for Xmap – Virtuemart so it turns green. Now VirtueMart should be availible in the Components menu.