to build a jmeter script with a liferay webpage

i need some help.. I´m building a script in jmeter, in order to access and fill some forms in a liferay webpage. I´m facing some troubles related with some fields, for example, to fill some textareas or even just select an option in a combobox. I´ve tried to record the actions, and also just type manually the parameters, but it doesn´t submit the fields during the execution. There is a different way to send these parameters?