Here is what you have to set in Forex Strategy Builder:
[Opening Point of the Position]
Bar Opening
Enter the market at the beginning of the bar
Base price - Open
[Opening Logic Condition]
Moving Averages Crossover
The Fast MA crosses the Slow MA upward
Base price - Close
Fast MA method - Simple
Slow MA method - Simple
Fast MA period - 5
Slow MA period - 15
Fast MA shift - 0
Slow MA shift - 0
Use previous bar value - Yes
[Closing Point of the Position]
Close and Reverse
Close all positions and open a new one in the opposite direction
Since Moving Averages Crossover is a logical condition only it determines the position's direction. The actual Entry point is Bar Opening.
The closing rule Close and Reverse makes the strategy reversable. It reverses the position avery time when MA5 crosses MA15.