The manual has a decent intro to synthesis, and breaks down each section.
A good way to learn is to play with each part of the synth separately. On page 14 of the manual is the "basic patch". You should start with that*, and pick a part of the synth you want to understand. When you get lost, or you want to try something else, always go back to that "initialized" state.
Even though the synthesis is subtractive, I find it is easy to make complex sounds(and know how I got there) by taking an additive approach with the available elements.
*Start with the saw oscillator at 50%, not maximum. As you tweak the oscillator section, and this is most noticeable in the triangle wave, you will see that going beyond 50-60% slightly overdrives the wave, changing its harmonic content and thus it's sound.