add docs for annotating an experiment

docs/evaluation/how_to_guides/annotation_queues.mdx

@@ -73,6 +73,9 @@ To assign runs to an annotation queue, either:
 
 3. [Set up an automation rule](../../../observability/how_to_guides/monitoring/rules) that automatically assigns runs which pass a certain filter and sampling condition to an annotation queue.
 
+4. Select one or multiple experiments from the dataset page and click **Annotate**. From the resulting popup, you may either create a new queue or add the runs to an existing one:
+   ![](./static/annotate_experiment.png)
+
 :::tip
 
 It is often a very good idea to assign runs that have a certain user feedback score (eg thumbs up, thumbs down) from the application to an annotation queue. This way, you can identify and address issues that are causing user dissatisfaction.