With any addiction or habit you want to change the most important part is not expecting it to just be done with, however hard you try. If you want to stop looking at porn all the time, then becoming someone who struggles with porn, and still breaks every couple of weeks is a big step. If you can keep that up for a longer time you might start being someone who breaks every three weeks and so on. What's tempting is to say "I can't do it, so why even try" and just give up.
Also, it's up to you why you want to stop a habit like that. Being conscious of your reasons and motivations can make it a postive step (whcih is easier to motivate) rather than just something you're preventing yourself from doing. When I was giving up smoking, it was helpful to think about postivies (breathing easier, having more energy, not stinking of smoke) because when I felt stressed and wanted a smoke telling myself "no you shouldn't" wasn't motivating.
It can also be helpful to identify the steps that lead up to a difficult decision point. If you're not wanting to look at porn, but you find yourself thinking "but I'll just look up some innocent pictures of blahblahblah, that's not porn, that's okay" and then suddenly you're in a situation that requires much more willpower to not fall down the rabbithole.
Good luck!
I'd agree with the other poster that maybe setting moderation goals would be a really good first step. I guess it depends if you're aiming for less masturbation, less porn, or less specific types of porn. And it depends on what level you currently find problematic.
For some people the problems with the addictivness of porn are linked to the dopamine hits of modern Internet porn, searching for the perfect thing, changing to newer / different stuff frequently. The a first step might be to continue to use porn when you need to, but your only allowed a single fairly tame video that you've downloaded. Eventually it'll feel boring and you'll it's not really just porn your craving, it's the whole dopamine hunt.
It's why vapes work so well for many people in giving up smoking. Nicotine is physically addictive and hard to resists, but also just getting your nicotine without all the other fun parts of cigarettes quickly makes it feel less tempting. It's much easier to give up something meh than something you're obsessed with.