for me I use the "pomodoro" technique. Pretty much you work for a set amount of time with full focus then have a 5-15minute break depending on how long the study interval was and then contiinue working. Theres lots of youtube videos that talk about this technoque and even some "study with me" videos in which you can study along side the person in the video using the pomodoro technique. I also find that chewing gum while studying weirdly helps haha
I use quizlet. Make flash cards and learn small bits of information, make sure to simplify don't make paragraph long flashcards. You can try taking a particular study design dot point and writing down (without looking at any notes) everything you know. Draw diagrams, write definitions etc. Once you've written out all you remember get your notes out and correct or add anything you've missed/gotten wrong. See what works for you, good luck!
If you're struggling to remember info, then definitely try Quizlet or making cue cards, mindmaps to link things to each other, and definitely trying to teach the content to anyone that's willing to be taught (if you can't get a friend). Being able to do that successfully will make the content easier to remember and show that you actually understand it.
As for applying this knowledge, doing a bunch of practice questions has worked for me. I've seen the difference that doing practice questions vs little to none can do on performance, so it's worth it. If just doing the questions and then looking at the answers isn't helping you improve, I've been trying to work backwards by seeing what the question wants from me before answering, then being able to answer more of those questions after.