Below are links to some of the many online tutorials for learning R.
Typically when you are “stuck”, it is a good strategy to use Google to find notes from other people who have worked through your same problem. If you phrase your search terms carefully, relevant results from Question/Answer sites such as StackExchange will appear and you can often get insights on approach, code examples, and be pointed toward other resources. If you decide to post a question yourself, use these guidelines.
Within RStudio you can read the documentation of any package or function that you have installed.
In the lower-right pane of RStudio (with tabs: Files, Plots, Packages, Help, and Viewer), click the Help tab and use the search bar to look for names of packages or functions. You can also search Packages and click on the name of a package to see its Help documentation.
For packages, the Help page will contain:
For functions, the Help page will contain: