There is an approach for locating an element using selenium.
First look for the ID then CSS Selector and then the XPath and then the Class Name.
Here is what I got from facebook both female and male have different ID and that is what you should be looking for.
<input type="radio" name="sex" value="1" id="u_0_9">
<input type="radio" name="sex" value="2" id="u_0_a">
Now that you know as how to approach the problem. I would suggest that you do the remaining thing rather than getting the complete answer.
Here is what I did
driver.findElement(By.xpath("//*[contains(text(),'Female')]")).click();
driver.findElement(By.xpath("//*[contains(text(),'Male')]")).click();