1st Step: Create a chart.

Click on Dashboard > Create a graph

2nd Step: Choose the type of graph.

Click on Select a data type > Bookings

Tick "Evolution over time" and select a type of graph

Then you can select the period you want to see the information from and if you want to see the information based on the session's date or the booking date:

Lastly, you can add additional filters for example to exclude canceled bookings from the graph to have more reliable information:

Give a name to your graph > Click on "Save"

Your graph is now available.