MUSE SCORE is a great, free piece of composition software with a vibrant learning community. Using notation software is an awesome, creative and fun way to really learn how music works.
There are lots of good tutorials on youtube. Here are some links to a couple of tutorials that I think are fairly easy to follow, and will give you a good understanding of how to use the programme.
Very in depth, 40 minutes long
A shorter series of themed lessons
A link to Muse-score's official youtube page; great for quickly getting the downlow on the latest updates and releases.
For those students who prefer to just read information, or who just want to get stuck into using the program and just trouble-shoot along the way, you can find the official (surprisingly readable) handbook here: https://musescore.org/en/handbook
Once you're familiar with the programme, and have started using it, it may be useful to learn some of the keyboard shortcuts to speed up your work.
Here is a complete list of all the shortcuts, but don't worry you won't have to learn them all - just the functions that you use all the time (adding extra bars, adding instruments to the score, adding chords or text etc)