how do you woohoo on sims 3 ??
xD ha you both relax on the bed & one of the options should be 'woohoo/try for baby' or sometimes if you do a lot of romantic actions the option would pop up under 'romantic'
Get them in bed relaxing, then click on the sim who you aren't playin an if there relationship is high enough. Woo hoo will be a option
if they have a good relatipnship you can click on romanticand then woo-hoo and then they will makeout and the go to bed an do it