Select the problem instance for which you want to validate a solution by typing or clicking on its name in the instance tab.
Create the solution XML file by filling in the form in the solution tab. Pro tip: you can directly copy the slot assignments from a spreadsheet (e.g. Excel) and copy them in the scheduled matches table of the solution tab.
Once you selected the problem instance and created the solution, you can press the validation button in the validator tab. Pro tip: you can also directly paste an instance or solution XML file into the boxes of the validator tab.