update readme

README.md

@@ -1,3 +1,25 @@
 # Peltier Jacket arduino to web bridge
 
-Just runit :)
+It displays temperature of the jacket
+
+# How to run
+
+## Setup
+
+Make sure that you have Python 3 and pyserial installed.
+
+You can install pyserial by using this command
+
+```bash
+pip3 install pyserial
+```
+
+## Run
+
+You have to give main.py one argument that points to the Arduino device.
+On Linux is is usualy `/dev/ttyACM0` or `/dev/ttyUSB0`.
+On Mac is usualy `/dev/tty.usbmodem.1412` or something similar.
+
+```bash
+python3 main.py /dev/ttyACM0
+```