As you've guessed, I'm a novice; truth be told, I've not tried to trim anything yet (except fruit trees and bushes, which I prune for fruit and also for shape (the latter according to my wife's preferences!). I decided to try to start growing some trees as a hobby during lockdown. So far, I have a few cotoneaster seedlings, about 4" tall, a sambucus, now about a foot tall, which I am realising might not be much good for bonsai purposes, a hawthorn, about 9" now, and 10 acer cuttings of various kinds. I've already lost some oak, conifer, hawthorn, whitebeam and hornbeam cuttings, so you can see I'm on a steep learning curve here! The conifer I started this thread with is one my wife gave me to play with, having had it a few years. I do like it and would not want to destroy it mindlessly, though if I could start to practice training it without killing it I would like to have a go. So any good advice would be very welcome here!
After a season or two when my trial plants have either succeeded or capitulated, I'll probably post pics and ask for more advice.