capture element of an option in JSF

I have a JSF code where, in the first place, you have to select an item from a list of options.
After selecting the element, another element that is a check, you must take the option that has been marked and from there take an action.

The problem is that I do not know how to capture the value of what we have marked in the option.

Check code:

<ice:outputLabel for="idTipoRegistro" value="Tipo de registro *" />
    <ice:selectOneMenu id="idTipoRegistro" label="Tipo de registro" 
     value="#{manifest.exp.docEnvioRegtel.idTipoRegistro}" styleClass="claseSelect">
        <f:selectItems value="#{manifest.exp.docEnvioRegtel.comboTipoRegistro}"/>
    </ice:selectOneMenu>

Code where I try to capture the option marked in the option:

<ice:selectBooleanCheckbox id="docuFisica"
 value="#{manifest.exp.docEnvioRegtel.codDocuFisica}" partialSubmit="true" 
 rendered="#{manifest.exp.docEnvioRegtel.codTipoInteresado == 'O' and
 manifest.exp.docEnvioRegtel.idTipoRegistro == 'S'}">
    <f:attribute name="docuFisica" value="T"/>
    <ice:outputLabel value="Enviar Documentación Física"/>
</ice:selectBooleanCheckbox>

This part is where I try to capture what I want.

manifest.exp.docEnvioRegtel.idTipoRegistro == 'S'