WildCard DNS and htaccess

I have been trying to work out how to set up wildcard DNS all afternoon. There's a heap of articles online, but they all say something different. I've had a gut full. So, since I am using WHM, I have decided to come here and ask.

Basically, I want a page like this:

www.mywebsite.com/p/USERNAME1/
www.mywebsite.com/p/USERNAME2/
www.mywebsite.com/p/USERNAME3/
etc..

to load at:

USERNAME1.mywebsite.com
USERNAME2.mywebsite.com
USERNAME3.mywebsite.com
etc..

I know as much as that I need "wildcard DNS". But trying to figure out exactly how to accomplish that has started giving me a headache. Can someone please just tell me where to go in WHM and what to change? Please? Before my face explodes?

I also know that's only half my problem. I've read enough articles to know that I will ALSO need a htaccess code to handle the actual redirection. If someone can help me make htaccess code that will allow:

USERNAME.mywebsite.com

to display the page from:

www.mywebsite.com/p/USERNAME/

..I will sincerely appreciate it. I know that there's people who can do the above in 35 seconds. I have so far been unable to understand anything in hours of reading. If anything, I have only got more confused, because EVERY article says something different, and I don't want to start messing around with DNS and explode my whole server, as well as my face. That's too many explosions for one guy in one day.