Custom report is created off data sources.
To design the report, first choose the data source you want to pull the data of the report from. Once a data source is chosen, a list of data column that is available is to be chosen in the list "Select Report Columns From Available Fields". Select all the fields that you want to show in the report (as columns).
Next choose the default fields to sort the report by.
Next specify the format of the report columns such as column title, data format, column totals.
You can create report filters to allow the report runner to further restrict the data shown in the reports. Filters are entered by the report runner during report run time. Report filters can be set up as ranges of dates , a single date, matching to some text pattern.
Click on Update the finish design the report. Go to the reports list and run the newly created report.