To spawn the particles in you are going to want to use this function

The first part of the function is the location that you will be spawning the particle at then its the size of the particle, it can be any number after that its the name, this will be useful when creating the particle itself. the two next parts are only if you want the particle to move if so then set the text to "move" and set the next part to the location that you want the particle to move to and last is the particle's lifetime so how long until it is deleted
WARNING if a particle is set to "move" it will have a chance to deform when spawning some, particles do this more than others so beware of this

Now I will teach you how to create the particles

To make a particle from a 16 by 16 image go to this website https://websim.ai/c/blCVjX28YA2WwJzAK and upload it then convert it to Minecraft blocks and you should have a list of blocks so make a skript with this code

then the variable name will be your particle's name so for this it would be called "particle"