For uploading your theme in VirtueMart, firstly you need to Install the VirtueMart on your Joomla platform. This can be done by using the VirtueMart plugin. So here are the steps to install a VirtueMart Plugin :
STEP 1: Log into your Joomla Control Panel and from top menu navigate to Extensions –>Manage –> Install.
STEP 2: As you select Install, a browse screen will open as shown below. From here, you can locate your Virtuemart zip file.
STEP 3: The com_virtuemart.3.0.14 zip file contains 3 zip files as shown below. You have to follow the correct sequence to install all these 3 files one by one once extracted. The sequence will be:
STEP 4: Once you installed all the three files; an installation success message will display on the screen as follows:
STEP 5: While Installing Plugin, you can also install the sample data that will include useful product features.
STEP 6: Installation is finished and now, you can see the VirtueMart Tab in the top menu of the control panel of Joomla.
STEP 7: You are all set for Uploading the theme/template that you created with TemplateToaster.