Instructions added

Added detailed instructions

README.md

@@ -28,5 +28,13 @@ chmod +x PiTempLogger.sh
 ```
 ./PiTempLogger.sh
 ```
+# Usage
+Upon running the script you will be presented with a menu. This is the place where all the main functions are listed.
+
+1. Run Temperature log: When selected a default log output file is created named *temp.tlog*. If you have changed the name of the output log by selecting option 2 from the menu then the log will be output accordingly. You will be asked to enter the *Log total time*, which is the total time the logger will run. After that you will be asked to enter the *Log Period* which is the interval between each log.
+2. Select the log filename: Using this option you can enter a specific name for your log. The prefix *.tlog* is automatically added. The output file is a tab seperated table which you can use as you wish. Changing output filenames during sessions can help you monitor your PI's temperature in different conditions(e.g. different emulators)
+3. View Log: With this option you can view the latest log. Using option 2 to change the output log basicaly switches between logs if they exist. So by entering a name for an existing log in option 2 will display that log when selecting option 3.
+4. Exit Logger: Quits the logger. It will ask you to keep the logs or delete them.
+
 ### Tested on:
 *This script has been tested on a __RPI3__ running __RetroPie__ 4.4.38-v7+ #938 SMP armv71 GNU/Linux