I'm trying to install a package through the R prompt by doing the following:
--- Please select a CRAN mirror for use in this session ---
You should either get a window with a list of repositories or a text menu with some options. But if that is not appearing, you can always specify the mirror from where to download the packages yourself by using
repos parameter. By doing that, R will not ask you anymore about the repository. Example:
Here you have a list of mirrors for R.