Follow the below steps:
1. Create multiple pages in the report i.e, one for report and a few for tooltip.
2. Once the pages are ready, Go to the pages which should be tooltip.
3. Go to format tab -> Page size.
4. Select the type dropdown and select the tooltip option.
5. Then convert the tooltip page to its actual size (tooltip size).[ View -> Page View -> Actual Size]
6. Now your tooltip is ready, now turn on tooltip from the format tab below the visualization shelf.
7. Go to the report, click on the visual that you want the tooltip to be shown and select tooltip from the format tab.