There is a lot going on here - can you clarify a couple of things for us:
- What version of R do you have installed?
 - What version of RStudio do you have installed?
 - Is your R version also using the Anaconda library like your RStudio version is?
 - Are you trying to install 
olsrrviainstall.packages()or some other way? 
If you are interested in using R via Anaconda, check out this thread - specifically @jcblum's caveats about using conda for R.
If you are able to install olsrr through R, the package should already be available to RStudio. If not, I suspect you have multiple libraries of R packages on your computer that are not shared between R and RStudio. I would be interested in seeing what the output of the .libPaths() function is for both R and RStudio.
I did just check on my computer and olsrr does indeed install correctly - I'm on the latest version of R and the preview version of RStudio v1.2 on macOS 10.13.6.