selecting a specific record from database

I need to create a table in which different user's data (it's an application) will be stored. One record line for each user, calling and inserting to be based on a single username. My question is this: How do you select a specific record of data from a table, and then call the data from that record alone. Additionally, how to enter the data into that table record. I am new to PHP/mySQL interactions, and I appreciate your help. Please reply to jeof@jeof.net if you can. Thank you! Jeof Oyster Top Flight Leadership