Merge pull request circleci#6549 from olukotun-ts/params-ui

Add section for triggering pipelines with parameters using the UI

Author: rosieyohannan

jekyll/_cci2/pipeline-variables.md

@@ -105,6 +105,21 @@ curl -u ${CIRCLECI_TOKEN}: -X POST --header "Content-Type: application/json" -d
 }' https://circleci.com/api/v2/project/:project_slug/pipeline
 ```
 
+### Passing parameters when triggering pipelines using the CircleCI web app
+{: #passing-parameters-when-triggering-pipelines-using-the-circleci-web-app }
+
+In addition to using the CLI and API, you can also trigger a pipeline with parameters from the CircleCI web app. To do this:
+
+  1. Navigate to the dashboard view in the web app.
+  2. Use the project filter to select the desired project.
+  3. Use the branch filter to select the branch on which you want to run the new pipeline.
+  4. Click the **Trigger Pipeline** button (towards the top right corner of the page).
+  5. Use the **Add Parameters** dropdown to specify the type, name, and value of your desired parameters.
+  6. Click **Trigger Pipeline**.
+
+**NOTE:** If you pass a parameter when triggering a pipeline from the web app, and the parameter has not been declared in the configuration file, the pipeline will fail with the error `Unexpected argument(s)`)
+
+
 ## The scope of pipeline parameters
 {: #the-scope-of-pipeline-parameters }