Search "hand ranging" or similar on YouTube. There are some good videos on there to help you.
However, I believe a good hand reader has to have a lot of experience.
I have been playing poker most of my life. When you gain experience, you become familiar with the way people play. Hand ranging becomes easy.
Start by asking yourself "what can I beat?"
Next ask yourself "what kinds of hands does opponent do that with?"
If he is repping A-K, does the story make sense? Did he raise preflop?
Review in your mind all streets of the hand. It is like a puzzle. All the pieces are there, you just need to put them together correctly.
And one of the most important factors to ranging someone is that person's table image. What kinds of hands do they play? Are they passive (very important)? Are they capable of a
bluff (surprisingly, people do not bluff that often)? Does their story make sense?
Here is an example:
Opponent opens for 4x preflop. Flop comes king high, rainbow. They check, you check.
Turn blank. Check, check.
River another king. Board something like K-7-3-8-K
Opponent now bets full pot. He checked 2 streets, but now he likes the king. Doesn't make sense. Unless he flopped a huge hand, and he is waiting for you to catch up.
You start your range preflop, and define it more clearly as the hand progresses.
LAGGY players are very challenging to range. They do not play ABC poker. TAGGY players are a bit more predictable. And fish/calling stations are fairly easy to read. If a fish raises you, you better have a strong hand to continue. They rarely bluff.
Bottom line is, experience is paramount to hand-read well. It is simply easier when you have been in a similar spot many times before.
Just my $0.02