The question in your title and in your content are two different things.
You can only get access to the Github repository for the enterprise code if you're an official Odoo partner. If you're not a partner you cannot access it and will only be available to download those files through the downloads page.
As for why you're getting the community version instead of the enterprise version.. You probably didn't add a link to the enterprise source code in your Odoo configuration file. You can find this file under /etc/ and is usually named odoo.conf. Add in the path to your enterprise repository there. It should look something like this:
addons_path = /opt/odoo/enterprise/addons,/opt/odoo/addons
Make sure that it loads the enterprise code before loading the community code.
i didn't find any addons like `/enterprise/addons` in the downloaded zip file.
Actually, i followed you script `https://www.odoo.yenthevg.com/installing-odoo-11-enterprise-ubuntu/'.
Executed your script and replaced the odoo module with the code of enterprise which downloaded from odoo website.
After replacing the code, when I run odoo as a service, the web page is not load.
In console i getting this error:
'XML Parsing Error: no root element found
Line Number 1, Column 1:
Tour Manager is ready. running_tour=null
Error: QWeb2: Template 'CrashManager.error' not found
Error: QWeb2: Template 'ActionManager' not found'