To calculate how much delta-V a certain amount of fuel gives you, use the delta-v calculator instead.
Dry mass: The mass of the payload you want to accelerate. Note that the dry mass must include the weight of the engines that will propel the payload, and of the empty fuel tanks that will fuel said engines (make a guesstimate).
Engine Isp: The fuel efficiency of the engine in seconds. Provided values are for vacuum.
Delta-V: The amount of velocity you need in metres per second (see the delta-v map). Note that the map doesn't provide good values for atmospheric take-off, because you need significantly more fuel to counteract the aerobraking (and how much more depends on the ascent profile).
Fuel weight: The weight of the fuel in tonnes.
Fuel amount: The units of fuel you'll need of the specified type.
Fuel type: The type of fuel you want to use.
We want to get the stock craft "Ion-Powered Space Probe" from the surface of the Mün into an orbit around it. We will need the following parts:
This gives us a total dry mass of 0.63t + 0.1t + 0.1t + 0.015t = 0.845t. The engine we chose has an Isp of 320kn in vacuum, and the delta-V map specifies that we need about 580 m/s to get from the Mün's surface into a 13km orbit.
As we can see from the calculation, one full Oscar-B should be enough to get us there. We can now repeat the calculation with a more accurate dry mass (one fuel tank instead of four) for a more accurate result.