I don't see anything that would prevent using SoundCloud.com as a download platform. You just have to enable it in the Permissions "tab" when you upload your music file or any time you edit it. You'd need a SoundCloud account, of course, but the basic one is free.
For YouTube, you have to create an account. If you have a Gmail address, you already have an account, but you can use any email account to set it up. Once you have an account, you upload your video file there and give it Public access. Done.
Creating the video is a matter of picking the right software, which may already be on your own computer. I used to do it with Windows Movie Maker, but I've heard that application has been removed from Windows. I would use iMovie or Photos on my Mac. But, basically, collect a bunch of photos (JPEG files) that you want to include, pictures related to your song theme, of you performing, I don't know, but have them sorted and in a folder in order. Create a "movie" project in your software app, drop all the photos in, add your song as the soundtrack, and then adjust the length of time each photo shows so you fill up the video to match the song. Usually you can globally apply a single transition, like a crossfade, to quickly finish things, and just add a title and fade to black.