Hey, sorry i'm your having trouble importing the package, do you know what unity version your using?
The import package for now only supports the standard unity shader pipeline not unity SRP or HDRP for the moment.
When impoting do you not get a package window link this?
You say there are some assets, if the Scenes are there like in the above one you should be able to just open one of them and play the scene to see the effect.
Thanks