There are different ways a publication can be made open access:
Open access journals
Three types of Open Access publishing options:
Unlike traditional copyright, Creative Commons licenses allow the creator of a work to assign a license which allows for specific kinds of reuses of that work.
To license your work with a creative commons license, simply place a statement somewhere on your work specifying what type of creative commons license it has, and link back to the Creative Commons.org website so that readers can view a copy of the license.
CC BY: “This license lets others distribute, remix, adapt, and build upon your work, even commercially, as long as they credit you for the original creation. This is the most accommodating of licenses offered. Recommended for maximum dissemination and use of licensed materials.”
All you need to do to assign a Creative Commons license to your work is to place a statement to that effect somewhere on the work. See the tab at left "Licensing your work as Creative Commons", or the Creative Commons Organization's website for more information.