Hi, go to the CRAN site and click on Download R for (Mac) OS X
If you are Catalina, download the package image called R-3.6.3.pkg because the alternative, called R-3.6.3.nn.pkg (regular) will not work properly.
If you are Sierra or higher, but not Catalina, select R-3.6.3.nn.pkg (regular).
You are right that you do not require a compiler, but beware of the following.
On macOS, packages sometimes fail to install, often with a non-zero exit status message. This is due to Apple's idiosyncratic compiler. The same packages will install on most Linux systems without trouble. Saint Simon Urbanek of the R Core Development Team takes on the brain damage required to recode the source to get around macOS's peculiar worldview for those in CRAN, but he can't bestow the same mercy on those still in development.
If you do not have the free Apple XCode App installed from the App Store` you will not be able to install any programs from source that require compilation.
Some packages will successfully install through compilation from source, but many won't.
When installing if you are offered the option to install from source, it makes sense to try it once. But, if at first it doesn't succeed, in all likelihood it never will. It's usually only 7-10 days until a macOS binary is available.
If you do want to install from source on the chance that a package may compile, in addition to the XCode app you need to enable command line tools from the terminal with
$ xcode-select --installxc