Sorry but I don't understand what you mean, you are not providing any additional information to help us identify the cause of the problem. (like the output of running library(ggplot2)).
In short, if you get the exact same error message then the ggplot2 package is not loading in your session, maybe you haven't successfully installed it as you think.
I don't know to use two geom in a single plot yet. But for scatter plot you can use the upto the two brackets and delete the rest from + , after the two brackets.