update readme

README.md

@@ -4,11 +4,27 @@ A C programming SDK for the TI-83 calculator. Includes pre-configured build syst
 
 ## Requirements
 
-- SDCC
+- A GNU/Linux system.
-- GNU Make
 - TilEm
-- RabbitSign
+- SDCC
 
 ## Status
 
 WIP.
+
+## Usage
+
+Initialise the build environment:
+
+```bash
+git clone https://git.palaiologos.rocks/Palaiologos/ti83-sdk
+cd ti83-sdk
+make init
+make
+```
+
+Run the pre-supplied program:
+
+```bash
+make try
+```