How would I go about making this?

How would I go about making a PHP script that gets data from a MYSQL DB and places the information within a Listview type table.. for example.

Column 1 | Column 2 | Column 3 |
Data1 | Data1 | Data 1 |
Data2 | Data2 | Data 2 |


etc.. etc..

but I want to also be able to go to say ?page=AddNew
and be able to submit data to the database as well.

I have a general understanding of how to do it but I'm honestly confused on where to begin :\.

Any bit of help is appreciated!