The forest deploy command enables you to apply some layout changes to your reference environment.
$ forest deploy --help
Deploy layout changes of the current branch to the reference one.
forest deploy
--force Skip confirmations.
--help Display usage information.

Deploying your changes

It is paramount to understand this command before using it:
As you can see in the above figure, the layout changes (Δ) located in your local branch my-branch will be irreversibly applied to your Production Environment layouts. Since your Remote Environment have Production as origin, the changes will appear there too.
To deploy, simply run forest deploy:
$ forest deploy
To be able to deploy, the origin of the branch should be the reference Environment (generally Production).

Deploy from the UI

This action is only possible for Remote Environments that have an origin that is the reference Environment (so generally Production as origin).
To deploy your latest layout changes from a Remote Environment, use the top banner link: "Deploy to ...".