You just have to place logo.png in the relevant folder and then run Artwork downloader, with local files set in the config options, and AD will add the logo to the Kodi db and then it should become available as long as the skin you are using uses clearlogos.
Good luck creating the logo, but you may have photoshop skills, I don't and have always failed making the relevant image transparent to be used correctly in Kodi. If you do know how to use PS or image software then could I please ask you think about submitting your logos to the relevant website and then if accepted it would become available through AD to everyone else.
www.fanart.tv would be the main one, but they are quite strict on the image quality etc. etc.
also check this thread
250984 (thread) user Shadowtek was kind enough to offer a service to create clearlogos but he no longer does unfortunately, but while he was kind enough to do it he created quite a few and you might just be lucky enough that what you are after has already been done. Again, just place the logo.png in the folder and use AD.
Also, just in case you are asking about logos for music, then check this thread
273287 (thread), usr Zag has been kind enough to offer a logo making service for music artists, if it is music logos you are after then you could always ask Zag if he could help you out?