How do I configure a phone extension number for a user? How do I install an extension in Vtiger? How do I uninstall extensions from Vtiger? How do I buy an extension from the Extension Store? How do I access the Extension Store? How do I set up my card details in the Extension Store? How do I update my card details in the Extension Store? Is there an option to write a review about the extensions in the Extension Store? Where can I find the Vtiger Inventory extension after installing it? Where can I find the Subscriptions extension after installation? Where can I find the Phone Calls extension after installing it? Where can I find the Forecast and Quota extension after installing it? Where can I find the Payments extension after installing it?