Required profiles: Analytics user, superuser
Only the owner of a report can edit it.
To use/edit a public report you do not own, or a system report you wish to customize, you can duplicate it by clicking on the hamburger menu in the top right corner of the report and select Duplicate.
Duplicating a report is a good time saver when you have to prepare similar reports along with report filters.
Note that the widgets in the duplicated report will be the same widgets. So if they have been "customized" it will be reflected in both the original report and the duplicated report.