Fill area between lines using ggplot in R

Welcome to RStudio Community.

Firstly, I'd really encourage you check out our guide for asking R-coding questions. FAQ: Tips for writing R-related questions.
It encourages to ask questions like this with a reprex. Right now, we can't replicate your code since it reviews to a file loaded from your machine. It's much preferable to set-up questions as an encapsolated reprex.

On this, your example is a little confusing. There are images with ribbons, possibly error bars. The code provided doesn't seem to refer to geom_ribben.

I'd suggest checking out the examples of geom_ribbon in the ggplot2 documentation,

For example;

huron <- data.frame(year = 1875:1972, level = as.vector(LakeHuron))
h <- ggplot(huron, aes(year))
# Add aesthetic mappings 
h + 
    aes(ymin = level - 1, ymax = level + 1), fill = "grey70") + 
  geom_line(aes(y = level))