Change VNet address space in Azure Cluster (Enterprise Edition)

Hi, I have deployed couchbase enterprise edition via Azure market Place. The components created there are Networksecurity groups, server, sync gateway and vnet.
I can see that the address space is by-default, and its not under the address space of our own defined vnet address space. This is resulting us in residing the default vnet outside our network, which we dont want.
Please suggest if its possible to customize the address space of the default vnet after it is created, if not what could be the workaround? If we can use our existing vnet instead of using the default one.