What is AndieGraph
AndieGraph is an emulator. It uses software to emulate the hardware found in your TI-82, TI-83, TI-83+, TI-85, or TI-86.
The source code found inside your calculator (the ROM) is owned by Texas Instruments and can’t be distributed. But similar to other emulators, AndieGraph needs this ROM to run. Without it, it’s useless. It’s analogous to having a computer without any Operating System installed on it.
Please obtain this ROM and place it on your SD card.
How to obtain a ROM
The only legal way to obtain the rom is to extract it from your own calculator. ticalc.org has an excellent guide on how to do that.
How to place it on your SD card
The proper name and size for your ROM depends on which model of calculator you own / wish to emulate. Please check that the file size is correct.
You will need to hook your phone to your computer via USB in order to transfer the ROM file to your SD card. How to do that varies slightly depending on which Android device and which type of computer you own. Let me google it for you: Samsung (use method 2), Motorola, Windows.