The general procedure of defragmentation your Windows Registry is described here.

1. Click on the "Defrag";   button to start defragging your Windows Registry in the Registry Defrag Screen.

Once Falco Registry Doctor starts defragging your registry, a status monitor will appear.

 

Once complete, Falco Registry Doctor  will inform you that defragging is finished.

To ensure the best results, please close all applications before you run your defrag.

During the defrag, your system may appear sluggish and to slow down depending on computer memory and the size of your registry.
This normal - do not attempt to stop the defrag.