Use this guide to set up your email provided by your internet service provider (ones like Road Runner, Comcast, Verizon FiOS, Juno, or CableVision's Optimum Online) to get delivered to your iPhone and allow emails to be sent using your account.
1. Click on the mail app (I'm assuming you've yet to configure anything, if not, go to email settings in the settings app)
2. It'll ask which type of email account you want to configure, for our purposes select "IMAP/POP"
3. Now, you'll need to type in your user name, password and the like - this information is exactly the same as the information in your email accounts.
4. Next, come the important parts - you'll need to set up the actual POP and SMTP server names, these can either be found on your PC's email client in "account settings", or if not, use this handy list and just find your ISP information.
5. Now that your server information is set up, just leave the port numbers the same (unless your ISP asks that you change them to something else).
6. You're good to go - click on the email account app and just watch your new emails come pouring in.