Very simple just keep buying gifts, playing the dating mini-game and giving the beauties gifts. The mini-game works like this:
The way the mini game works is that you need to zoom into their face and body. Every so often you need to look away to avoid the meter on the right from dropping all the way. When the brain meter on the left fills up you will prompted to give them a gift which in turn fills up the heart meter at the bottom center of the screen. After a few gifts the meter fills up and you get to have sex with the beauty netting you a gift.
By giving them gifts and sleeping with them you can eventually unlock: