There are several schemes for making presentations with R markdown.
I like to use the
xaringan package (others include ioslides and beamer).
To make an xaringan presentation, install the package then (after restarting RStudio) go to File > New File > R Markdown > From Template > Ninja Presentation.
This will open a draft document showing some of the features you can use.
Knit it, then start to edit it.
Everything you have learnt above about formatting R markdown documents, code chunks, figures and tables for documents applies to presentations.
New slides in
xaringan are made with three minus signs.
There must not be anything else on that line (not even a space) or it will draw a horizontal line instead.