Familiarize yourself with the basic TI-84 programming commands. Study the syntax, function and access methods for the "DISP" command---the command that lets you display custom text messages on the screen. Look at the menu screens for choosing the most useful functions. Use the web page, titled "Texas Instruments: TI-84 Plus Guidebook" to study the different commands, different key sequences and different program menus.
Use the virtual TI-83/84 calculator at the Texas Instruments: Module 13 web page, listed in the reference section below. Follow the example in the tutorial to assure that you always enter in the correct key and program menu sequence necessary to start using the program editor and program TI-84 code correctly.
Design your program flowchart, an ordered list of steps and decision steps that you will follow in your program. Convert and write down these steps in TI-84 program code; use the Texas Instruments TI-84 Plus Guidebook pdf file (see Resources) to help you decide on specific commands to use, their proper syntax and how to locate them in the TI-84's programming menus.
Start programming with the TI-84 by first hitting the "PRGM" key. Next, select the "NEW" option to enter a name for your program. Press the "ALPHA" key to type alphabetical letters for the name of your program, one letter at a time. Press the "2nd" key and then the "ALPHA" key so that you can continually type in letters without having to press the "ALPHA" key before you enter in each individual letter. Using the letter labels above the keys on the keyboard as your guide, enter the name of the program and press "ENTER" on your keyboard. Type the program code into the program editor that appears. Use the program editor's menus to select commands and the ALPHA key to either type letters or numbers as your code dictates.