Ah - I see. You have a web server and DokuWiki running on your personal PC at home and now you try to make the DokuWiki on your PC visible to other people.
Well there's a short answer, given your knowledge and your experience in computer networking: Do not do it! Don't even try! Why? Before your friends have found their way into your Wiki, you will have gathered a large group of new 'friends', some living in Russia and other places, all making free use of your Wiki and, indeed, your server.
What are the alternatives?
For one, you could find yourself one of the many free web servers where you can run your own copy of DokuWiki. Those servers are all ready to be shared in the internet, and all the difficult things have been supplied by the operators of those servers. Some are even said to offer a ready-made installation of DokuWiki.
On the other hand, if it's just about sharing a few documents over the internet, a Wiki of your own might be a bit of overkill. For that use case, you might consider one of the many cloud services offered, many for free. My favorite is pCloud, but there are a great many services available. I am prejudiced against Google and Dropbox, but even those would be better for a rank novice than trying to run his own web server at home.