I don't think you can use RStudio "desktop" on a chromebook.
However, you can use a browser to connect to an RStudio Server.
One easy place to do this is Rstudio.Cloud - try http://rstudio.cloud/
If you need your own RStudio Server, then you'll maybe need to setup a server yourself - this is slightly harder but I think there are some good blog posts around for this - e.g. look for container versions of RStudio Server and for how to host them on e.g. AWS.
Good Luck