Hi
Kirsten. It might be good to get what the word Remix actually means first. The word remix does not mean remixing a song. It actually means you take elements from something that alreday exists and build a whole new piece of (very original) music around it. That is important to know.
A good place to practice remixes is Indaba Music.
https://www.indabamusic.com/ When you get there click on 'Opportunites' There are tracks there that can be remixed. You can hear the original track with all its parts etc. But you can register (free) and once you do that you will have access to all the individual tracks that made up that total original mix. Then you can load them up in your DAW and get into it.
Another option is to go to this website here:
http://www.cambridge-mt.com/ms-mtk.htm This is the website for Cambridge Music Technology and is the work of Mike Senior. Here you can download lots of multitrack sessions. You can listen to an MP3 file of the music (mixed) before you download so you can get an idea of the track. You could practice on these too for remix practice. You could also just practice using these to get your basic mixing skills up and running too. Hope that helps.
You can do Google searches for things like 'Best Remix Tutorial Videos' and you will turn up things like this:
http://www.musicsoftwaret...xing-walkthrough-info/ This is a good before - after example of a remix. Also if you do YouTube searches for similar things you will turn up a lot there.
It might be good to get some basic skills in Music Creator as well as
Herb is suggesting below.