First off, Jungian Analytical Psychology is a FULL system.
Identifying the unconscious in oneself is something that requires time and experience.
I know I have Ji (Dom) and Ni (Aux). These are obvious for me to identify. If you really want to be able to identify your Unconscious Functions, you DO NOT look at your thought process AT ALL. That is like trying to tell a joke saying "Why did the chicken cross the road?" And your audience giggles and says "Why?" and you say "IDK". To put it simply, it is a very very bad joke. So what does that leave us with? The answer is to look at your behaviors, specifically, you have to ask yourself "What are my unhealthy behaviors?" This is not easy because it is a humbling experience that forces you to identify your weaknesses. Furthermore, "Typing" yourself is NOT a trivial thing. When someone asked Jung what psychological type he categorized himself as, he basically said "I have thought about this question a lot, and it is a painful experience."
Personal example: I know that I have Unconscious Se. How do I know this? Because I am a smoker and I drink a lot of soda. Those are things I do that effect a physiological response i.e. sensory stimulus, which manifests itself in an unhealthy way because they are harmful to my own well being.
OK, so if you want to know how I know I have Ni as Aux, this is relatively trivial in comparison from me being able to discover Se is in my Unconscious Functions. I have not read the entirety of "Psychological Types", but what I have read, I can say to pretty high confidence levels that I actually understand what Jung was getting at. Along with this, If you look at the Functional Illistration I made on how Functions manifest themselves in People according to Jung, what I was able to intuite about how they work was almost completely 100% correct according to someone who understands Jung's works far far better than myself in part because they have studied Jung for a much longer time period than me and reading things about Jung that I probably could not even recognise as something that came from Jung.