Go to Reports in the menu on the left > select which report template you want to edit. In the menu bar, select the icon called “Add new graph”. Finish by click on “Save”.
In Boardeaser Beta it looks like this:
Go to "Reports", click on "Unpublished". Click on the icon with three dots., select "Edit" on the report you want to edit.
In the menu bar, select the icon called "Add new graph". You can choose to add multiple graphs to a report. If you want to save your report click "Save" or if you want to preview your report "Save and show".