1). Start Internet Explorer and verify that you are able to load the following URL:
https://cran.rstudio.com/bin/windows/contrib/3.2
Change the URL so it matches the URL from the warning message. If you cannot access the URL in Internet Explorer, you may need to go to Internet Explorer > Tools > Internet Options > Connections > LAN settings and configure a proxy, or otherwise make sure you have a working Internet connection.
2). Once you have verified that Internet Explorer has access to the CRAN/TRAN repositories, start the TERR Console and run the command setInternet2(TRUE) before proceeding with the package installation:
> setInternet2(TRUE)
> install.packages("dplyr")
3). If the previous step failed, open Internet Explorer, go to Tools > Internet Options > Security > Internet, and lower the security level.