After installation simply comment /rebase to trigger the action:

Due to current limitations of GitHub Actions:

GitHub Actions is limited to private repositories and push events in public repositories during the limited public beta.

Rebase action currently only works on private repositories since it requires IssueCommentEvent event.

To configure the action simply add the following lines to your .github/main.workflow workflow file:

workflow "Automatic Rebase" {
  on = "issue_comment"
  resolves = "Rebase"
}

action "Rebase" {
  uses = "docker://cirrusactions/rebase:latest"
  secrets = ["GITHUB_TOKEN"]
}