The first sentence says "The current release of Bioconductor is version 3.8; it works with R version 3.5.3.". As James mentioned, old versions of R and Bioconductor are not supported. This means that you have to update your R to the current release.
But do note that we don't provide support for outdated versions of packages, so you are on your own if things don't work as expected. All things equal you should just use the current versions of R/BioC.