Install ROOT 6 on OS X El Capitan

Dear experts,
I’d like to install ROOT 6 on my new MacPro (OS X El Capitan, version 10.11.4).
My intention is to install the binaries (root_v6.06.02.macosx64-10.11-clang70.dmg).
Should I install something BEFORE running the dmg? The laptop is new and the environment is clean.
Can you help me? I have no experience with Mac…
Many thanks in advance

The pre-requisites are documented here:
You need to install Xcode (from the App Store) and also install the command line tools running in a terminal xcode-select --install
Opening the .dmg file (double click) will show you the installer document (.mpkg). If you double click will not install because of the security preferences by default. Right-click and select “Open with…” and select “installer (default)” and then “open”.