trying to make a wavy edge I'm a beginner in blender and was looking around for learning the basics. I found some videos on youtube (https://www.youtube.com/watch?v=f5Gb1VK98Wc) (the last 10 minutes have what I'm trying to do) and at the end of one a donut is made but the icing is supposed to be wavy on the edge. so when I select the bottom layers and put the setting on random and pull down there are no waves being made. rather the entier layer is stretched down and the top half gets wavy. then when I hide the top half and only use the bottom row of vertices they still just get stretched downwards. any and all help is greatly appreciated!
Two possible scenarios:

Did you select every single vertices on the bottom ring? If so, stop. Just select one vertex when using the proportional editing tool for this. Use the scroll wheel to increase the fall off of the proportional editing tool.

Do you have the subsurface modifier enabled? If not, the random function will make it jagged.