Start at the home page for the entire OTN forum web site
See the category that is named Oracle Database?
Right-click that and open the link in a new browser page or a new browser tab (your choice).
That will show you a list of absolutely every current forum related to Oracle's database products.
ApEx is the sixth forum in that list.
Go back to that home page for the forum web site.
See the `+` sigh in front of the words Oracle Database?
Click on that to expand out the first layer of topics.
See the choice that labeled "More"? Select that.
You end up at the same view as with the first method I described.
Nether method is particularly difficult.