Position, scale, and rotation: These all have X, Y and Z fields that will help you move the emitter around in relation to the camera (position), how far in each direction the particles will go (scale) and at what angle (rotation). You can play with the values of these fields (positive and negative numbers) to create the effect you want.
Emitter: You can choose what type of emitter you want to use. Since I have a fixed background—it will not move if we move the camera—I'll use the Ring emitter, which will spray particles in a spherical radius. This will create a "world" effect that will make some particles appear closer and others further from the camera.
Customizing particles: The Birthrate determines the number of particles the emitter will release. The more particles you want, the higher this number will be. Speed, Scale and Lifespan, are self-explanatory—the first one determines how fast your particles move; the second: how big your particles are; and the third: how long your particle will last before it fades.
Force: This is like gravity. If you play with the values in the Y axis, you'll notice your particles will appear lighter or heavier. A value of 0.05 will slow your particles down—the lower the value, the heavier particles will be.