First of all you must have an opportunity to connect to some local or remote InterBase/Firebird server. Besides you need your computer to satisfy the system requirements of EMS Data Comparer for InterBase/Firebird.
Please refer to How to register EMS product for details.
The trial version of the utility allows to compare and synchronize no more than 10 tables. As for the rest, the functionality of the trial version does not differ from the full one. You can test the features implemented in Data Comparer within the 30-day trial period for free.