How should I start my game?

The basic behind my game is a 2D game with 4 different classes.
-Gunner
-Specialist
-Sniper
-Grenadier
Each class has it's own attributes.
There are up to 2 players and each player has it's own board. There is a board with two sides A and B.

The players select the same number of classes, but can decide what ever classes they want. Each class does different damage. When all classes are killed, the player wins, yada yada yada.

How should I start this....? I'm kind of at a stand still. Also should I use N++ or Eclipse for this. Thanks