We're expanding the "It's Better in Lightning" learning prompts so you have even more tools to get your users working faster and smarter in Lightning Experience. Starting May 1st, 2018, a new prompt displays when users who have the Lightning Experience User permission view dashboards in Salesforce Classic. To help your users learn in context, they can switch to their dashboards in Lightning Experience and see exactly how things work in the new interface.
You can control the learning prompts that users see to best support your org's Lightning Experience rollout. From Setup in Lightning Experience, type "Onboarding" in the Quick Find box, then select Onboarding & Assistance.
To learn more about the "It's Better in Lightning" learning prompts, check out Encourage Users to Work in Lightning Experience (https://sfdc.co/qNpvO) in Salesforce Help. The topic covers who sees these prompts, how frequently they appear, and what users experience.