Ensure you have defined the themes you want to track and uploaded your data and then select 'Heartbeat' from the main sidebar navigation.

Click the blue plus button in the top right and complete the required fields, then click 'Create Heartbeat chart.'

Click on 'Select data' and choose the relevant project and timestamped data file (also known as Language Set).

From the drop-down menu, select the relevant theme.

Add the name and description and click 'Create Heartbeat chart.'

Drag and drop the things you want to track into the theme builder side panel or select from the saved themes by clicking the drop-down menu.

Click the Heartbeat icon in the side panel to apply those themes to the data associated with your current comparison.