I guess you mean acces the user interface...

you should be able to acces the user interface here https://23.239.28.158:8069 I guess (:8069 indicates that you will be using port 8069 [which is the default port odoo is using] to acces the url 23.239.28.158).

If that does not work you can try to start start the server manually like this (assuming odoo is installed in /opt/odoo/odoo-server)

sudo server odoo stop   (to make sure odoo is really off)

su odoo    (assuming there is a system user odoo on your machine)

cd /opt/odoo/odoo-server

./openerp-server

All this should work whether you have installed odoo from github. I don't know whether anything is different whether you used the so called nightly builds and installed them by using ap-get commands

In most cases one would use a script to start odoo and probably it would be set to be autostarted when the OS starts. If you have followed any of the poluar installation guides you probably have such a script (which should be located in /etc/init.d and be called oddo-server) and such an automated startup mechanism

Of course this also assumes you server is accessible from the 'outside'. Which might be a given for a cloud hosted machine