Set up discount code promotion on Magento store (seems to have an issue)

We have a magento(1.7) based store with subscription billing and want to create a discount coupon scheme such that customers with a particular discount code will be charged £0 for first month and full price from next month onwards.

Not sure if there is an issue here but we cant seem to find the top level Promotions tab in our Magento panel.

Need some one with good experience in Magento to fix the issue and set up the discount code scheme for us.

Please reply to us with a fixed price and estimated time for the project.

Thanks!