But the answer is there. It depends on your own risk tolerance.
1. You may move the SL to breakeven as soon as the signal is in positive territory, effectively reducing your risk to zero on that particular trade, but then your stop will be taken our more frequently by market volatility.
2. Or you may want to wait until the signal is in significant profit (that is, 300 pips or more) and only then move the stop to breakeven. Even so it happens sometimes that the price retraces to the entry level, hitting your stop, but not so often of course.
3. The third possible tactic is leaving the stop at the original -300 pips. FYI I follow this one, but for you as a new subscriber I would recommend that you follow the second.