To activate the package, you need to add

  (pdf-tools-install)

somewhere in your .emacs

Next you probably want to take a look at the various features of what
you've just installed.  The following two commands might be of help
for doing so.

  M-x pdf-tools-help RET
  M-x pdf-tools-customize RET

 -- Rémi Vanicat <vanicat@debian.org>, Sat,  9 Dec 2017 08:40:08 +0100