Mix.install cannot be used inside a Mix project?

Questions & Help Questions
1

I am trying to install extra libraries into a running instance of elixir app. The app runs inside k8s container. I remote shell to the instance with kubectl exec -it then at the prompt:

bash# iex --name ddd@127.0.0.1 --cookie cookie --remsh app@127.0.0.1

and the I do this:

iex(app@127.0.0.1)1> Mix.install([:recon])
** (Mix.Error) Mix.install/2 cannot be used inside a Mix project
    (mix 1.14.0) lib/mix.ex:513: Mix.raise/2
    (mix 1.14.0) lib/mix.ex:656: Mix.install/2
    iex:1: (file)

I do not understand what this means? Can anyone explain what it means? Why mix project is special? And if there is another way to install a dependency?