newbie: how to set up disc quota for each user a volume

Hi,

I'm trying to set up a 4.5 gb disc quota for each user on my servers 250 gb hd. Unfortunately, I have a very poor knowledge in this. So my question is, how do I set up a disc quota in an easy way? Is there any programs for that (I tryed webmin but it crashes all the time). Or how do I do it manually (easy, cause' I'm a poor newbie)? I'm planning to have round 50 users on my server that will backup their files by smb/afp.

thanks in advance

--celerity