Two minutes, once. After that the app reminds you — you don't have to remember to open anything.
Checking…
It has to be Safari. Chrome and Firefox on iOS can't install web apps — that's an Apple restriction, not a bug here.
At the bottom of Safari — the square with an arrow pointing up.
It's in the list below the row of apps. You may need to scroll a little.
Top right. An ATS Tasker icon appears on your Home Screen.
Not from Safari — from the new icon. Then come back here and turn on notifications.
Apple only delivers notifications to web apps opened from the Home Screen. Stay in a Safari tab and you'll get nothing — no morning prompt, no evening prompt — and there'd be no way for the app to tell you.
Chrome can install it directly.
If nothing happens, open Chrome's menu (⋮) and choose Install app or Add to Home screen.
Works fine in a browser tab — desktop browsers deliver notifications without installing anything. Installing just gives it its own window.
Look for an install icon in the address bar.
One nudge at 10:30, one at 18:00. No escalation, ever.
Install it to your Home Screen first — follow the steps above, then open the app from the new icon and come back.