When the money management window pops up (by right clicking on any chart) enter say 5,000 in Capital, this represents your balance with the broker. In risk you enter the amount of risk that is acceptable to you against that 5,000 capital.
Say you enter 3% in risk you will then see the risk value change to 150. i.e. 150 being 3% of 5,000
Now lets say that you have found a trade that you want to take but it requires you to place your stop value 30 pips away from the current price. Now enter 30 in stop value and then in the bottom window you will be given the amount of money you can trade at per pip to stay within your 3% risk setting. In this case that would be 5.00