The recorder range is a little over two octaves. The recorder notes, or more to the point, where the fingers go when making them, are shown below.
The thumb hole is at the top left of each diagram. For the higher notes, the thumb hole is shown half open, like this
Only 10% or less of the thumb hole is actually open for these notes. "Cracking" the thumb hole, or getting the opening just right is a key aspect of recorder technique.
Moreover, each recorder note needs the right breath pressure. The low notes, G and below for the alto, D and below for the soprano won't sound properly if the breath pressure is too much. The higher notes, C and above for the alto, G and above for the soprano won't sound properly if the breath pressure is too little. In particular high D and F for the alto (A and C for the soprano) need the breath to be exactly right.
Some of the recorder notes have alternate fingerings, these are shown on the diagram. These alternate fingerings are used for trills, and also make some difficult passages easier to play. The top F# for the alto (C# for the soprano) needs the bottom of the recorder to be covered, usually done with the knee. Take care that your knee does not bump the recorder against your teeth...
The recorder lessons on this site outline these techniques in detail.