Hi Ivan,
do you mean for testing purposes? Then you can use transaction WE19. Select one sample IDoc as a template (or just select the IDoc type and fill it with the values that you want), set the receiver port in the IDoc control record, so that it will be sent to your external system, and then you can click "Start Outbound Processing" and set the "repeat factor" to as many IDocs as you want to fire to the receiver... 
Best Regards, Ulrich