We used to show DD by using on ourself first. Or her teddy would take a puff to show her it didn't hurt.

There were sometimes when DH and I had to hold her down while she was kicking and whatnot because she was having an asthma attack and didn't want to have her puffer but needed it.

DD has had a puffer since she was 2. At 4 she was ok with me giving her a puff whenever she needed it.

Also we use a silicone face mask on the spacer to make it easier.

I know it can be frightening to watch someone with asthma (my brother had severe asthma growing up, was constantly in hospital.)
Have you gotten a pack from the Asthma Association?
I know Asthma SA hold classes/lectures for parents and others. Maybe your local association does too?