Sure a javascript(which you can add in the javascript tab of your form) should work:
//AUTO GENERATED CODE, DO NOT DELETE
(function(){var javaObject={
//YOU CAN PUT YOUR CODE BELLOW
//jQueryFormReference:A jquery reference of the loaded form
AfterFormLoaded:function(jQueryFormReference){
rnJQuery('#rnField46 .rednao_label_container').append('<label style="display:block;font-size:12px;color:#5f5f5f;font-style:italic;">Test description</label>');
},
//jQueryFormReference:A jquery reference of the loaded form
//formData:An object with the information that is going to be submitted
BeforeFormSubmit:function(formData,jQueryFormReference){
//Here you can put code that you want to be executed before the form is submitted
}
//MORE AUTO GENERATED CODE, DO NOT DELETE
}; return javaObject;})
all you need to do is change rnField46 for your field id (which you can find in the advanced tab of each field settings). If you want to add many descriptions like this you can repeat that line to add more than one description like this:
rnJQuery('#rnField46 .rednao_label_container').append('<label style="display:block;font-size:12px;color:#5f5f5f;font-style:italic;">Test description</label>');
rnJQuery('#rnField47 .rednao_label_container').append('<label style="display:block;font-size:12px;color:#5f5f5f;font-style:italic;">Test description 2</label>');
Regards!