Hi.
I have found over the years, especially with students who are new to computers that fear of breaking something or getting it wrong hampers the ability to learn.
The best thing about computers is that they are very good at giving you fall back positions or undoing mistakes, if you are made aware of it.
The most important thing then is to save what you are doing regularly.
Control S or Apple S. This then gives you the option of reverting to your last save (in nearly all software) if it suddenly all goes horribly wrong.
Even in the commercial world you'd be surprised at the amount of people who don't do this and then lose everything.
The other brilliant thing on computers is to be able to undo the last thing you did (some software will enable mutlitple steps backward).
Control Z or Apple Z. this keystroke will undo the last thing you did - brilliant.
So remember, don't panic, you can revert to a last saved version or undo the last thing you did.
Possibly two of the most useful things to learn.
All the best
Dave