GitHub link from Issue to Wiki

You can also use relative paths. Here's an example from one of my projects:

[Using-a-Shell-Configuration-File](../wikis/Using-a-Shell-Configuration-File)

I prefer this approach to full paths, since it's not impossible that you might rename a project or transfer ownership to someone else, and so break any absolute references to parts of the repo.

Use [text](link_to_wiki_page) where link_to_wiki_page is the full URL of the wiki page you want to link to. Just navigate to the page and copy/paste the URL from the URL bar.