Install Gitlab CE on existing digital ocenn drolet with apache 2.4

how to install Gitlab CE on below configuration:
Ubuntu 14.04 64 bit
Apache 2.4

I have digital ocean droplet already setup and I am planning to run Gitlab on external url like

You’re going to have a much better experience if you use a completely brand new droplet and set your Gitlab service up with the Omnibus installation package and its included Nginx web service.

Not to say that you can’t host Gitlab with your existing Apache service, but the configuration is going to be quite a bit more complicated.