How do I increase the initial position/spread of particles in Niagara

It’s my first time messing Niagara particles (v4.23). How do I increase the spread of particles? I’m making a rain particle (converting it from Cascade). I want it to spread, basically change its initial position such that it has a bigger area, more spread in x, y (and possibly z) to spawn from. I’m changing the Emitter Spawn -> Emitter Properties -> Fixed Bounds -> Min & Max values in the Particle Emitter & then add the particle emitter to the particle system. However the particles don’t spread further from the original area. How can I do that? In Cascade, you simply expanded the Initial Position. Now in Niagara this is giving me trouble. Any help will be appreciated. Thank you.