> install.packages("DESeq2")
Installing package into ‘/home/z800/R/x86_64-pc-linux-gnu-library/3.2’
(as ‘lib’ is unspecified)
Warning in install.packages :
  package ‘DESeq2’ is not available (for R version 3.2.3)

Does it mean I need download R version earlier?

use

source("https://bioconductor.org/biocLite.R")
biocLite("DESeq2")

or download it from here to your computer and install it.