Why is Dynamic Material Instance not working :(?

alright i understood all but one thing

what is a name named material slot and how do i make it?

**-Edit-
i found it and did what you told me to but it only affects the emitter i placed in the blueprint in order to link it to the “Create name dynamic material instance” and i doesn’t affect the emitter i spawn using “spawn emitter attached”

how can i make it apply to a spawned emitter?

and also it changed the emitter itself there is a reason or i did something wrong?**