Nothing to be nervous about. Although a relatively delicate, precision instrument, an airbrush is a tool, just like any other tool, and can be used with ease. OK, we've all harped on about practice, but this is logical - there are some people who think buying and using an airbrush will make them better modellers/artists/nail painters whatever, and that their models/paintings/nails will therefore be wonderful overnight. Well of course, that's not going to happen, and an airbrush is not an essential tool, more a convenience and, to an extent, a luxury.
What we have all been offering is some advice to allow you (or any other newcomer to airbrushing) to commence work on a model with at least a little confidence, brought about by practice and familiarity with the tool, rather than gross disappointment and frustration, after attempting to use the tool, straight out of the box, on a model.
Think in terms of only ever having used a hand drill and sand paper, then being given a variable speed power drill and a power sander, and told to make a wooden cabinet - without first finding out how the power tools work.
The airbrush is a similar thing - find out how it works, why it works, where it works and how best it works - in differing situations and requirements - the you'll have the confidence, and basic ability, to use it 'for real' when you come to tackle your first model paint finish with it.
The rest, like anything else, comes with practice and experience.
So - get stuck in !!