I need some help

I think

1. Go to a manga
2. Choose one of those options: want to read, reading or already read
3. Scroll trough options to bottom and click "subscribe"
4. When manga updates, a red note will appear in ur top right corner of this website

Hope you will get it :)

Do you mean how to make the manga's updates get notified?
For that you need to go to the main page of the manga (the one that shows the title and cover, OR the page that shows when you finish reading the last chapter (the one with people's comments and recommendations).
You need to look for three buttons: "Want to read", "Now reading" and "Already read".
Then you need to push the "Now reading" or de "Already read" (the want to read one doesn't work for notifications).
A little panel will be shown, you can choose some options, but you don't need to. You go to the bottom of the panel and push on the "Submit" button.
And that's it.

if you're talking about the notification appearing right after the update: you can't change that. the notification will only pop up after some hours and i heard it depends on your timezone. if you mean that you want notifications to appear when a manga is updated (in case you're not getting any) i'd recommend you mark the manga as "want to read" or "reading".

i'm not sure wether this is what you asked for lmao but i hope i could help you a little bit (=・ω・=)

Correction to step 3.:
the subscription button is the third option

and the option only appears when the manga is ongoing, clear why I think

^^

To those who say that they should click on "want to read", I think it is wrong. At least that's what says the little help besides the notifications section:

How to activate manga update notification function?

The manga you add into READING or READ list, will automatically activate manga update notification function.

For example, I want to receive the update notification of "You're My Loveprize In Viewfinder". I'll mark this manga as ‘Now reading’ or ‘Already read’, then when this manga got new chapter I'll get the notification.

OMG thnx I have been looking for this for ages

Thnx actually the only thing that is showing up on my notifications is solo leveling and I have no idea how I did that

Thnx for the information

Ur welcome! Happy to help :D

u're welcome :)