The Parallels provider is used just like any other provider. Please read the general basic usage page for providers.
When Parallels provider is installed it has a higher priority than any other provider shipped with Vagrant. In most cases you will not have to specify the provider name, just "vagrant up" will be enough:
$ vagrant init parallels/ubuntu-14.04 $ vagrant up
But if you have a multi-provider configuration and/or want to be sure that
parallels provider will be used, then you can specify it explicitly:
$ vagrant up --provider=parallels