more specific instructions on creating files

slides/slides.Rmd

@@ -127,7 +127,7 @@ tinytex::install_tinytex()
 # Creating Documents
 
 1. Create an R Markdown document.
-  - R Markdown documents are plain text.
+  - Use the `New R Markdown` file option in RStudio, or create a plaintext file.
 2. Run the R code
 ```{r, eval = FALSE}
 rmarkdown::render({document.Rmd})