If you are referring to iReport 3.5.0 then the resultant jrxml file cannot be used with Servoy plugin due to different libraries being required. You can try to specify the ".jasper" file produced by the 3.5.0 iReport with the Servoy plugin - I have had some success but it is not always going to work if some feature new to iReport 3.5.0 is not in the library (jasperreports jar file) for the Servoy plugin.
I have a request in to rebuild the Servoy plugin for iReport and JasperReport 3.5.0 but that will not be immediate. Best is to try to use the iReport designer for 3.0.0 and the Servoy Jasper plugin (unless my trick with using the jasper file type works out of iReport 3.5.0).
Sorry if that sounds complicated.