Hi, and welcome!
Please see the FAQ: What's a reproducible example (`reprex`) and how do I do one? Using a reprex, complete with representative data will attract quicker and more answers.
readRDS() opens a file in the serialized rds format, usually containing data. It has nothing to do directly with ggplot2.
The first thing to do is to confirm that ffile is in your working directory:
dir()
If you don't see the file, that error message would appear.