Please forgive me if this question has been asked already, but a quick search on the forums turned up nothing. I have no experience in editing Wikipedia except from fixing errors in the text. I want to write about my Player Characters and add them to the Player Character page, but I don't know how to add images to the Character Infobox. I know on the template, it says "| image = " and that I put the name of the image I want to add there, but how do I actually upload the image to the site?
That's quite simple; have a look at the sidebar on the left of the page and scroll/look at the bottom of it. You'll find the "Toolbox" with, amongst other things, a link to the "Upload file" page. After that you just need to follow the instructions on that page and then add the filename you uploaded it to in the | image = field on the charact infobox, as you've already found out.
PS: Another tip is to look at the MediaWiki documentation first when you're unsure how to do anything on the Wiki. Nearly everything is documented better there than I can explain it to you;
here is the MediaWiki help page on (adding) images, for example.
Ah, thank you. I was trying to find a help page like that, but it never showed up for me.