The %>% operator (the magrittr pipe) can't be found because it's not in namespace (the term for recognizable objects). This can happen if the related package hasn't been installed and if it hasn't been loaded. The pipe is in the {magrittr} package. Installing packages is done the same way that you have done with {lubridate} and the others at the top of the screen. But that's not enough. You must also invoke it with
library(magrittr)
directly or, indirectly, with
library(dplyr)
which is the usual option.
One way to pick up the most often needed packages is with
install.packages("tidyverse") # needed only once
library(tidyverse)
which will load {dplyr} (including the magrittr pipe) and many, although not all, of the other packages you will be using routinely during the course.
When you come back with other questions, use a reprex (see the FAQ) to illustrate problems rather than a screenshot. You're likely to attract more answers that way.