The following are all useful and free books, available to read online:
R for Data Science, Workflow: Basics Chapter: http://r4ds.had.co.nz/workflow-basics.html
Modern Dive, Getting Started Chapter: http://moderndive.com/2-getting-started.html
R & RStudio Basics: https://bookdown.org/chesterismay/rbasics/3-rstudiobasics.html
RStudio IDE Cheatsheet: https://github.com/rstudio/cheatsheets/blob/master/rstudio-ide.pdf
ggplot
refresherR for Data Science, Data Visualization Chapter: http://r4ds.had.co.nz/data-visualisation.html
Modern Dive, Data Visualization Chapter: https://moderndive.com/2-viz.html
RStudio ggplot2
Cheatsheet: https://github.com/rstudio/cheatsheets/blob/master/data-visualization-2.1.pdf