How Do I use frame Data when Pressuring a blocking opponent?

Ok, so It’s been some years since I was first ever introduced to fighters. the very first thing I played was mk9 ( the game had no frame data and since I had no internet at the time I was unaware it was a thing) when I was probably 13 now I’m 18. and It’s been a long journey of game study, terminology learning, and professional play examination, ever since I actually decided I wanted to become a decent player.

my end goal is to win a tournament no matter what the size of it, Then move on to something big. in the end I imagine myself joining a team of other gamers to prepare for future tourneys…basically to become a pro at all costs…

The game that I’m best at and have grown to love is injustice so up until Injustice 2’s release I’ve been preparing by practicing on injustice 1.

Personally, I feel confident in my footsies, execution, BnB’s, and optimized combos. But one thing that I finally have to do is actually use the frame data… this is probably very simple for some but I never actually used it in any fighter. By becoming experienced with matchups I simply used just whatever I knew came out faster than my opponents attack. but for Injustice 2 frame data and canceling things to make them “safe” is a must for competitive play. and Its not like I don’t understand it because I do. I simply don’t use it and because of this I’m at a loss in Applying It

I Feel like this is the last thing I Have to understand before I can truly start on this path (and move on to reading tactics and baiting even better players into situations).

So my question is how do I pressure. and how can frame data be used to help in this? (I know what pressuring is. and I see how others do it effectively, it looks so easy then, but whenever I’m In the moment I’ll just throw out some random combo and end it with a special attack meter burned. but this is really predictable and I feel I’m not doing it correctly)

The situation now is I’m working to get money to buy a new ps4 since the original was broken by my sibling. I already have my copy of Injustice 2, I have a list of characters I feel are best suited to me. and I play injustice daily practicing in the lab running through tech, and every character possible not only learning everyone’s abilities but what makes the core of the game.

My current character list for Injustice 2 is as follows

Joker (I love his setups and unpredictability)
Scarecrow (I love the character and slow and sluggish is my bread and butter. lol I mained Solomon Grundy back in the old injustice days)
Gorilla Grodd (He just looks dangerous overall and I hear he is execution heavy so it gives me a chance to show off without mouthing)
Brainiac (My favorite character in this game. Brainiac has great abilities for mobility and decent setups)
Starfire (not out yet but I love this character and I’m willing to learn her) I’m crazy about the Teen Titans

Two I like also are Dr.fate and Robin. I played my copy long enough to get a good understanding of doctor fate (went over a friends house). and Robin just looks like he’ll be good to learn now rather than get beaten by later.

I know all the Leauge characters because a majority were in the first game
Superman, Batman, Aquaman, Wonderwoman, Flash, Black Adam, Cyborg, Bane, Harley Quinn, Catwoman, Joker, Green Arrow and Green Lantern (I especially favor Green Lantern and Joker)

What I’m trying to say is i have enough knowledge of things to go straight into ranked confidently but I need to get my pressure done correctly. (I know I’m gonna lose…ALOT…But this is what makes learning fun, correcting mistakes and returning stronger)

Like Sonicfox said "Injustice made me Sonicfox"
In my case it made me obsessed…so much so…that I want to prove a point…
(it is also for love of the game)