How do I add css to a child theme?

[Hannykaahs]

I have seen the instructions on wordpress.org for child themes, and I have a bare bones child theme that someone gave me, but because I don't know css very well, I'm not sure how to start. I am usually able to make the css changes I need to in a regular theme, but now that I'm working in a theme that will have updates, I need to put my css edits into a child theme. What I don't know is the proper format to add those changes into the child theme. Are there detailed instructions anywhere on how to do that? Or should I just post here what I'm trying to accomplish and then someone can tell me what I need to add to the child theme?

I saw something that referenced child theme tutorials but I am unable to find any.
thanks for the help.