Click on the blue New Task button. A new window opens.
Select Delete files as Action and enter the file paths that should be deleted as Payload. The example below will delete all files in your /server/rust folder that end with .map or .sav and all player .db files. You can also add other file paths, e.g. from oxide plugins. /oxide/data/backpacks/* for example would delete all files and folders inside /oxide/data/backpacks. Click on the blue Create Task button, if you are done.
Done! At the end your schedule should look like this: