In order to start an interactive RStudio session on one of the login nodes, you would first need to connect to the cluster with X11 forwarding enabled. Afterwards you need to load the modules required by RStudio and then you can start the session with the command rstudio.
[sfux@eu-login-08 ~]$ module load new legacy gcc/4.8.2 mesa/12.0.6 rstudio/0.99.669 Autoloading openblas/0.2.13_seq Using OpenBLAS build of R-3.2.2 [sfux@eu-login-08 ~]$ rstudio
Please note that you should not run any R jobs directly out of RStudio. If you would like to run an R job, then you need to submit it through the batch system.