Honestly this is hard for me (another noob) as well. Even when i look at a hand i didnt think i played well, i often dont know what to look for and how to approach it. There is a lot of free stuff online, but a huge part of it just tells you what to do without focusing on why (for example, a lot of strategy videos on youtube are just guys reading solver charts to you without explaining much). What i ended up with is that i can fit an explanation to pretty much any play, and explain with smart poker words why it is good, but i often dont know which play is actually good and which is me working back from the answer that i want to give intuitively or emotionally. It is exacerbated with the lack of time during play (on ACR thats 15s per action + 30s timebank for your whole game at the table pretty much). This often results in my thinking process being, lets put it nicely, messy during the hands i play.
During the analysis, i try to focus on these hands where i didnt think it through, didnt have time or didnt know what to do. I go action by action, asking myself the same questions i try to think about during play, but with more time and less emotions - like whats the opponents range, who has range/nut advantage on the board and by how much, what hands am i targeting with my next action (ie what im trying to fold or get value from) etc. If i dont know the answer or the hand in general makes no sense, i look for information online (there is really a lot of free content out there). I also found that writing my thoughts and actions down helped me realize where i was wrong (i was going to post a hand for analysis, but while i was typing i realized that it was crystal clear that i played it wrong). You can post hand histories in this forum too, people are really helpful.
For putting people on ranges, you usually go by process of elimination or working backwards and looking at the action. The most basic examples are preflop - lets say you raise utg and the villain calls in the big blind. You know that he should have a range with a lot of hands, but he probably doesnt have complete junk like T6o nor his best hands like AA, KK, QQ, AK etc - he would have probably 3bet those (you can look up optimal ranges in a lot of places online). Now when the flop comes AsKh9d, you bet and he calls, you know that he probably doesnt have 8c4c anymore - he might have a pair (including Ax, Kx, 9x or a pocket pair), 4 combos of 2pair w Ac9c, Kc9c, As9h, Ks9s, pocket 99 for a set or some kind of a draw. Etc etc. Of course, you adjust the "good" ranges if you see that your opponents deviate from normal play. If you know your opponent is a nit and would not raise with anything but aces, he might have KK on the flop. If your opponent is a loose passive fish who doesnt have a fold button, he might call on that flop with 86o etc. I wouldnt adjust the ranges that you put your opponents on too much from the norm though, except for the most egregious cases.
I also really liked this post that i found that helps you learn to think on a basic level:
https://forumserver.twoplustwo.com/6...l-50nl-367707/
Good luck