While sheet music can look complicated at first sight, it's easier than you think. Like scales music notation is pattern-based. Learning to read it is simply a matter of learning to see the patterns. You can learn enough to begin reading note values in just a few minutes.
Sheet music represents notes using the staff, a set of 5 lines and 4 spaces. The lines are numbered from bottom to top, line 1 at the bottom and 5 at the top.
Notes are defined relative to a root note, and this root note is itself defined the clef, a symbol placed at the beginning of every line of music. As a player of a melody instrument you will be using the treble clef (left). You will have seen this symbol before as it is frequently used as an ideogram for music.
The treble clef states that the note G may be found on the second line of the staff. For clarity I have highlighted it in red:
What's the circle around the line? This is a 'note.' Circling the line G tells you to play a G on your instrument. On an ocarina in C you would use the following fingering:
When I first tried learning to read music the above symbol was confusing. I had a mental image of a 'note,' a circle with a stick attached. If you're in this position stick with me as this will be covered in more detail below.
OK, so circling the second line tells you to play a G, but there must be more to it. After all music would be pretty boring if there was only one note. The other notes are defined relative to this point. If a note circles the space below the G line you take one step down the scale. The music now tells you to play an F.
If a note circles the bottom line, you take one more step down the scale to E. The note D hangs of the bottom of the staff, touching the bottom line.
To place C you must imagine that the staff has extra invisible lines with the same spacing. C lives on the first of these. To hint the lines existence a short strike is placed behind it, which is called a ledger line.
From G the same pattern may be continued upwards to F, the highest note playable on an alto C ocarina:
Practice notes using this tool:
As was mentioned above this simple circle might not align with your mental image of a 'note'. In fact in the earliest forms of sheet music this circle was the only symbol used. Over time people wanted the ability to include the rhythm in their notation. In order to do so additional symbols are added to the circle.
Every note includes a circular 'note head' as shown above. Some notes include a 'stem' which is a vertical 'stick' attached to the circle. The stem may include one or more 'flags', like the two notes to the right.
The different designs of stems and flags represent how long the note will be played for.
As you can see all notes have a head, but they don't all have a stem. Regardless of the shape of the stem, or lack thereof, the line or space which the head 'circles' determines the note that we should play. All of the following notes are all G. I have grayed out the stems to highlight the similarity of the heads.
There is more to it, such as rhythms (note stems), key signatures and style notations (slurs, staccato marks). Like determining the value of a note as described above they are also straightforward, following simple logical patterns.
In the beginning you don't need to be able to sight read fluently to make use of sheet music. Due to the massive volume of music available in the format there is a good chance you can find what you want to play. Consequently there is a lot of value in simply being able to 'decode' the letters of the notes. Even doing this you're still practicing the notes on the staff. After you do so for a while you begin to know a notes letter at sight.
The same thing applies to matching fingerings to the notes on the staff. To begin with you'll have to look up every one, but over time this too will become automatic. Look at the note on the page and think of it's letter. Next look at the fingering for this note letter in your fingering chart. Place your fingers as shown while looking at the staff.
Once you get some practice reading sheet music is actually easier than reading tabs. Instead of having to process the positions of every finger, you can discern where the melody is going by reading the shapes formed by the notes on the page.
For example, the following shows two instances of a common pattern; play a note, play the note above, then play the starting note again. First from G, then again from high D. As you progress you will be able to play such patterns without caring about the named value of a higher note. You just ascend to the next note in the scale, then drop back down again.