Don't forget to update the source code of this HTML form in order to list in the destination_addr options the address you are using for your ESME. I'll be a good idea to use your own destination address if you plan to use the SMSC simulator I mention below.

Check that the IP address in the form action points to your SMPPSim SMSC simulator.

If you don't want to set up a SMSC simulator on your own, you may keep the default action IP address, and use the simulator I usually have running on that machine.