Before restoring a backup file there are some important things you need to know.
First when you restore the backup all of the current data in Informant will be overwritten with the backup data.
Second if you have experienced a total data loss and your data has not been restored after you have performed the restore operation from a backup file that is an indication that your Informant was configured to use the iOS calendar data which is not backed up in Informant, if this happens to you please contact support.
To restore an Informant backup please go into the Informant settings, backup/restore, select the backup file you wish to restore, then select restore from the options.
If you are syncing your data and choose to restore from a backup file rather than repopulate Informant from the sync service you could cause your data to be duplicated. Syncing after restoring the data from a backup file will duplicate all like items that existing between Informant and the sync service that you are using. We advise when possible to recover your data from the sync service.
If this is not possible and you are concerned about duplicating your data please contact support.