Confused about the law on sampling

Hi all,

I'm pretty new to producing, so apologies if this is a silly question.

I'm a little confused about sampling and the law about it. In a lot of hiphop tracks (Take Kanye West for an example), they use alot of samples from old soul songs. Now if im wanting to make and sell beats that have samples on like that, do i need to get permission from the copy right owners? Does that mean Kanye went and got permission for all those samples? How on earth do you even get permission? Cheers all