In general you need free slots for attending hoes, otherwise you get the option to replace a current one.
The process of getting the option to offer a slot to a hoe is done via dating a girl from iSnatch successfully and then increasing her interest by fucking her several times (here you can find her at the fuck buddies list). When you reached max commitment you can offer her a job.
Alternatively you can acquire a hoe from another pimp from the street. Here you have to take 'offer her a job' button and win the fight against the opposing pimp. The results here are not very convincing, but maybe a good start for a newbie.
Have fun ;-)
