Pull request labels

In your Account Settings, you can configure Release to create environments through the use of Github labels.
Find GitHub Settings at the bottom of the Account Info tab in Account Settings.
The "Create Environments by applying labels to Github PR's" is automatically turned on and defaults to a label named "Create Release Environment". You can change the label name if you wish to, then click the Save button.
In GitHub, create a new label that matches the label you saved Release. If you're unfamiliar with this process, please refer to GitHub's managing labels documentation.
Adding a Label in Github
Add the label to the pull request and Release will create the environment. If you have comments, statuses, or deployments turned on, Release will update the pull request with information as your environment is created.