I was a mature student and so understand that there can be some questions/anxiety about returning to study, but you don't need to learn how to study before starting a course.
If it's at access to/degree level, the university website will have tips and information on developing study skills, note taking, and even how to read efficiently.
Set time (and a place?) for study
Discipline - limit distractions to maximise focus
Listen and take notes of main points
Re-read and organise notes directly after a class
Use different highlighter colours to organise/separate different points
Apply as necessary, Who, Why, Where, What and How, to answer questions fully
There are also tips/tricks like playing background music at a certain tempo that stimulates the brain when studying, and even looking at a candle flame to train focus.
I was capable of focusing totally on an assignment for 12 hours at a time - a friend says I'm a bit OCD but I'm just not easily bored which means that I can binge watch a tv series for hours at a time!😜
I also found that I could "rest" by switching to a different subject as this kept my interest level from falling and allowed me to study for longer periods.
What sort of study level are you contemplating OP?