VirtueMart is a Joomla extension, which makes installation straightforward. Before you install VirtueMart, however, make sure you are running Joomla 2.5. VirtueMart is currently not supported with Joomla 3.
Install Virtuemart in Joomla!
1) Download VirtueMart from the VirtueMart website.
2) Extract the zip file you just downloaded, there should be 2 zip files:
com_virtuemart.2.0.14 (install this one 1st, it contains the Virtuemart component)
com_virtuemart.2.0.14_ext_aio (install this one 2nd, it includes all the additional plugins and modules required to use the Virtuemart)
3) Login to your Joomla! Dashboard.
4) In the top menu, click Extension Manager option.
5) Under the Upload Package File menu, click the Browse button.
6) Navigate to the first file (com_virtuemart.2.0.14), and click the Open button.
7) Then click Upload & Install. This may take some time to complete.
8) You will see some information listed, and possibly a warning, we will address this in the next section.
9) Under the Upload Package File menu, click the Browse button again and navigate to the second file (com_virtuemart.2.0.14_ext_aio)
10) Click the Open button.
11) Click the Upload & Install button to the right. This may take some time to complete.
12) You will see a notification upon completion stating “Installing component was successful.”