Some tips that I can make are...

1. Employees like gifts. Give them something to remember the training event. Perhaps a pen with the project logo or credit card holder or a pouch to keep their receipts. You need not spend too much on it.

2. Make help easy to access. Communicate links to access training material, names of super users and administrators. Perhaps even intranet forums where employees can help each other and modes to make suggestions. Conduct refresher training for new joiners and those that wish to revise their knowledge.

3. Publish results of groups of employees (like departments). There is nothing like competition to foster adoption.