The relationship between the 2 sims must be very strong enough for a woohoo. Have both of the sims relax on the bed, and click either sim for woohoo, or have both sims in a car and click and sim then woohoo
No you can't, but Sims can "WooHoo". To do this have two Sims in a romantic relationship relax in a bed, and select "Cuddle" and then "WooHoo in Bed" or "WooHoo". You can "Try for Baby" on The Sims 2 for PC/Laptop by doing the same thing, but choosing "Try for Baby" instead of "WooHoo".