I need Certify as Apple Mac Technician. So How can I access ATLAS ?

ATLAS training and certification is managed by your employer. Ask who is the ATLAS contact within your HR department.

In this article from which you came ( How to access ATLAS - Apple Support ) is this statement:

To access ATLAS, you need to have an active Global Service Exchange (GSX) account. GSX accounts are limited to technicians working at Apple-authorized service facilities.

It appears there is no access for a free-lance technician. In spite of the link at the bottom of the ATLAS support pages, there is no support for ATLAS in these communities, which consist of other end users.

We are fellow users and Apple is not here. Click the Get Support button at the top of this page and ask an Apple employee.