Yes, you can manually enter the results for each run.  On the Add Run Data screen, simply type in the results and click on the Save button.

The User's Manual is the program's help file. This contains all of the documentation on how to use the program. There is also the information in these FAQ's to help you out.

If you want a printed manual, you can view the help file and then click on the Print button to print a particular section or the entire file.

Make sure that you have setup and tested your timer in the Hardware Settings screen.

Normally, to start a heat, you would click on the "Ready Timer" button.  For a heat that has already been run, that button will instead say "Rerun".  Just click on that button to rerun the heat.  You will get a warning asking if you want to reset the times, and then you will run your heat as before.

If you are inputting results manually, just make the necessary changes before you save them.  If you had already saved the changes, you can delete out the incorrect run and add a new run.

As Derby Data Tracker has the same hardware interface as GrandPrix Race Manager, please refer to the GrandPrix Race Manager Hardware FAQ's.