How do I get activities to show up in the records I imported in Sales in the Redwood User Experience?

You must run the Publish Feed Elements process to enable the Activities (feed) panel and subview for the records you import. The process publishes the indexes required for the Adaptive Search to track activities for all the objects that have activities enabled, including leads and opportunities. You can't run the process separately for individual objects.

To learn which records the process updates and how to run it, see the topic: How do I enable the list of activities in each record in Sales in the Redwood User Experience?.