The WP Bakery plugin is included in theme package and so you can install it directly from wordpress dashboard. You do not need a licence key. In every theme update, we include the latest versions of all included plugins as well.
To update visual composer plugin, please read more here.
If you have already bought it on your own, then we can not guide you on licence key issues. You have to contact plugin’s support.
What contact form are you using? If you are getting spammed, we suggest to install ReCaptcha in your contact form.
