The five-line staff
The staff is five lines and four spaces. A note is a dot on a line or in a space, and its height is its pitch — higher on the staff, higher in sound. That's the whole foundation. Reading is just working out which line or space.
The shape comes first
When the dots climb, the tune goes up; when they fall, it goes down. Before you name a single note you can see the shape of a melody — and the shape carries most of the music.
Position is pitch; shape is length
A note also has a shape — filled or open, with a stem or a flag — and that tells you how long it lasts. That's Stage 2. For now, one job: position on the staff = pitch.
The usual mistake
Reading a stack of notes as separate puzzles instead of one moving line. Your eye should follow a melody like a path, not stop dead at every note.
Try
Violin down. Trace the notes on this page with a finger, following the line up and down, humming the shape. No names, no bow — just the contour.