1.  I have my sketch in a file called "mysketch.pde" . How do I load and run it in Simuino ?

Answer: 
    Start Simuino. 
    Enter "conf" to see current configuration. 
    Enter "conf sketch <path>/mysketch.pde" . Be sure to give the path relative to simuino directory.
    Enter "load"  or "load 700" if you want a simulation of length 700 steps.

    Now, if your sketch is without errors, you shuld be able to analyze by stepping. Enter "run" to be in Run Mode. 

2. Text  [Errors -err] is displayed above the curser. What is this ?

Answer:  Something went wrong when you loaded the sketch. Enter "err" to see more information in the message window.
    Most likely, your sketch is not compiling and/or sketch is not according to Arduino rules:
            - writing or reading a pin in wrong mode (INPUT/OUTPUT).
            - Read or write values exceeding limits
              etc. 

http://web.simuino.com/faq