You can select the location you wish to view up in the top left, you'll need to know its name or the three letter CRS code. You can also change the train companies you wish to see - the codes are in the format as given by ATOC. It is possible to change the date that you are viewing, but you will need to do that in conjunction with the time column.
You can change the window in which trains are shown using the upper drop down box, the two lower boxes are to allow you to set your own time if you want. If you do pick your own time, you can change the date where it normally says "Today" on the left.
You can change the filtering of whether all trains, just those calling or passing are shown in the top box. In the lower box, you can change it to see all, passenger or non-passenger trains.
You can restrict trains by STP indicator - this represents the type of schedule. They are explained below: