Backup your files first!
As with any disk-clean up project it is always best to have a recent backup - preferably on a different drive or in the cloud.
What type of scan?
Duplicate Cleaner Pro has several types of scan it can run: Regular Mode, Image Mode and Audio Mode. Regular mode will find duplicates by comparing the actual content of the files, or by attributes such as file name, date and size. Image mode compares the content of images to group similar pictures, or can compare image tags. Audio mode compares the tags embedded in audio files.
Select your scan mode and set your criteria on the Search critera tab.
Note that if you select too many criteria such as same modified AND created date, Duplicate Cleaner may not find any matches. If in doubt, try a first scan in Regular mode with just 'Same Content' checked.
Where to scan?
Tell Duplicate Cleaner where to scan on the Scan Location tab. You can use one or more paths/drives as a starting point.
As a quick side note it's best not to scan and remove the entire drive containing your Windows system and Program files as removing these can break your system. Duplicate Cleaner is designed for your own documents and data, not for cleaning system files.
Starting the scan
Click on the 'Start scan' button on the Search criteria tab or Scan location tab. A scan may take minutes or hours depending how big the drives are and how many files we are searching for. Network speed may also be a factor for remote drives.
After the scan
The Duplicate files list is displayed upon the scan finishing. This is the list of all the duplicate files found. They are arranged in numbered Groups (Shown in the group column). Each file in a group can be considered duplicates according to the criteria you set at the beginning of the scan. Marking (ticking/checking) a file specifies that you intend to remove (delete) that file later on. Note that this list contains ALL copies of each file, so you should leave at least one in each group when removing files.
Duplicate Cleaner has a tool called the Selection Assistant which can help you automatically select files.
You can use the selection assistant to help select files for deletion (for instance "Select all but one in each group", or "Select files with the lowest bitrate". To select earlier versions of the files you could use the 'Select oldest files in each group' function.
You can then use the 'Remove files' button to delete or backup elsewhere the files you selected. Always be careful though, and be sure you have a backup before starting!