@monroemann
1.) Tell us, which template you are using! If you use f.e. the dokuwiki-template you find the logo in "/Users/Heiner/Sites/wiki_colibri_HV/lib/tpl/dokuwiki/images/logo.png". The first part of the location will be different at you. If you have direct access to the file directory, just replace that logo with your own and ensure that the webserver is allowed to read it.
2) If you do not have direct access, just try to upload the new logo via Media Manager to :wiki:logo.png or directly to logo.png! It is really described in detail by the link, Andi provided you with. (I hope) I have quoted the most important stuff.
3) Send your avatar which you are talking about to
virk@gmx.net!
Changing the Logo
Here are the locations checked by the template code:
The site's logo
:wiki:logo.png
:logo.png
lib/tpl/dokuwiki/images/logo.png
Please make sure that those namespaces (either root or wiki:) are readable to all users. Otherwise the image will be broken to users who are not logged in.
Kind regards
Heiner