Click the "New Build" button in the web UI for the buildkite-bash-example-pipeline
pipeline.
Or you can use curl:
curl -H "Authorization: Bearer $TOKEN" \
"https://api.buildkite.com/v2/organizations/test-org-ldnicolasmay/pipelines/buildkite-bash-example-pipeline/builds" \
-X "POST" \
-F "commit=HEAD" \
-F "branch=master" \
-F "message=First build :rocket:"