A line near the bottom of the screen often has messages from the pine program that you must deal with before it will let you move on. If pine won't respond to your commands, check this first. Run the command by typing the letter. Pine creates folders in your account. You can tell it to create other ones, too, if you want a filing system for your old mail.
New mail is in the inbox.
When you start pine, you are put in the inbox. To read a particular message, use the arrow keys until it's highlighted, then hit return. The default folder is saved-messages, or you can tell pine to make another folder to keep it in. Saving your messages in a folder other than the inbox helps save space on the mail server computer. Use the arrow keys to move to the appropriate one, then return.