Each JIRA Project has it's own Wiki section.
To browse the different projects, simply click on the "Wiki" dropdown in the main JIRA header.
Click on "Browse Projects", to navigate to a list of the project Wiki's you have access,
along with an overview of how many pages each project contains.
Clicking the name of a project leads to the "Project Home" screen, which will show you
any pages you've recently viewed, or have marked as favorites.
Clicking on the page numbers leads directly to the "Page List" screen, which will show
you all the active pages within the project.
If the Wiki dropdown in the main header already contains the
project you want in the "Recent Projects" section, you can
simply click it there, and it will lead to the Wiki of that
project as well.