If Stop_Loss is set to 0, the EA will not use a stop loss. If Stop_Loss is set to 1, the EA will automatically determine the best stop loss for you. If Stop_Loss is set to any number other than 0 or 1, that number will be used for the stop loss. Stop_Loss is always set in points, regardless of whether you are using a 4 or 5 point broker; a Stop_Loss of 500 would always equal 50 pips.
I strongly recommend that you do not use a stop loss. The EA is not a "pray for return" EA it will cut losses. Exit strategies are often more complex than a simple hard stop. If you use a hard stop, the EA will still be profitable, however the win/loss ratio will not be as good. I only recommend using a stop loss if you are trading with higher lots and need to better define risk.