UNREAL UE4 - Niagara - How to start Niagara´s paticles at 100% and freeze movement?

Hi, i want to créate clouds with Niagara particles, the problema is that these particles need to be freezed from start… and i have no idea how to achieve this, they always start from cero to 100% and they keep moving… i need this particles to appear already at 100% from start and not move, stay freezed forever so i can use them as clouds, i preffer this method tan actually make tons of spheres and apply materials, because its more random and i might add other effects like collisions or slight movemment, BTW… i have no idea ow to “key” for Niagara animations.

Please help!