To create a custom report, head to the 'Analytics' module. In the 'Trend Analysis' tab, you can start to build your own report with the sites and meters you have loaded into the platform. 

On the left hand side of the screen, you should see the navigator. You can use this to select which meters you wish to report on - and there's no limit on the number you can select. (Make sure the relevant utility is highlighted in order to see the meters you are looking for.)

Once you have chosen your meters, you can choose a date range and date resolution for your report, switch between a bar graph, line graph or heatmap and add overlays and lots of other useful features to your report.

When you are happy with what you have built, select 'Add to Report' in the top right corner. Here you can choose whether you want to append your chart to a report you made earlier or create a brand new report.