If available in Hex, the package can be installed as:

1. Add ex_do to your list of dependencies in mix.exs:

```elixir
def deps do
  [{:ex_do, "~> 0.1.0"}]
end
```

2. Ensure ex_do is started before your application:

```elixir
def application do
  [applications: [:ex_do]]
end
```