How do I change network settings in Vagrant?

The config.vm.network... part is what you want to write in the configuration file instead of running it with the command.

After executing vargrant init, Vagrantfile appears to be created in the folder where you executed the command, so open it in any editor and rewrite the required parts (follow the instructions on the referenced page).

Note:
Vagrantfile-Vagrant by HashiCorp
Summary of frequently used Vagrantfile settings

As far as the screenshot goes, what you're running at the command prompt is a command that doesn't even have config.vm.network.That's why I got an error.

The command to execute after vagrant init is usually vagrant up.

When vagrant up runs, as Cubick said, the contents of the Vagrantfile are loaded and the vagrant works with the virtualbox accordingly.