Go to https://www.vagrantup.com/intro/getting-started/install.html and download the relevant package and install.
Vagrant relies on interactions with 3rd party systems, known as "providers", to provide Vagrant with resources to run development environments. Examples are VirtualBox, VMware, Hyper-V.
I chose VirtualBox because it was first on the list and I am using a Mac :)
Go to https://www.virtualbox.org/wiki/Downloads
https://www.virtualbox.org/wiki/Downloads
and get your download and install.
*You may run into an issue with the install on Mac
$ vagrant init bento/ubuntu-18.04
$ vagrant up