A video is not necessary, although we understand seeing someone do it might initially sound like it's easier.

First, we should clarify for you some of the common language/terminology used in your synth.

As musicians when we say "transpose" we are referring to changing the key we are playing in. But with a synthesizer, like your S90 ES, that is both a keyboard controller and a synthesizer tone generator, it can take on two separate meanings.

The S90 ES makes a distinction between the term TRANSPOSE and the term NOTE SHIFT. Here's why:

_ TRANSPOSE is used when you are talking about data that is *transmitted* either by the Keyboard or a Track of the Sequencer.
_ NOTE SHIFT is used when you are talking about a PART that is *receiving* data... From the keyboard or a track of the sequencer.

If you TRANSPOSE the S90 ES, you could, for example, make it so that when you pressed the F above middle "C" it sent the message that caused all connected devices think you played C3 (middle C). Transposing causes all receiving devices to think that middle C was pressed even though you actually played F3.

If, however, you change the NOTE SHIFT parameter of the tone generator, only the sound is moved. For example, you press F3 (the F above middle C) you could Note Shift the receiving Part so that it plays Bb4... All other devices see F3 the actual note you pressed, only the receiving tone generator Part will be changed and play Bb4. Anything connected via MIDI would still see F3 the actual key you pressed.

TRANSPOSE is transmitted and is a function of the Keyboard or Seq Track. Transpose affects what goes OUT via MIDI
NOTE SHIFT is a function of the receiving device. Note Shift affects only the internal Tone Generator, and does not affect what goes OUT via MIDI.

So to put the ball back in your court which do you want to do?
Which mode are you in. Voice, Performance, Multi?
What do you want to accomplish?
Since there are several ways to proceed we need to customize the answer for your use case.

You will find a NOTE SHIFT and a TRANSPOSE parameter:
Press [UTILITY]
Press [F1] GENERAL
Press [SF1] TG (Tone Generator)
Here you can globally change the S90 ES's response

Press [SF2] KBD (Keyboard)
Here you can globally change the S90 ES's keyboard transmitting Out

You will also find NOTE SHIFT as a PART parameter in PERFORMANCE and MULTI modes. Where each Part can be set individually. Say you need to "shift" the bass sound up an octave in a split you are creating, or lower the string an octave while keeping the layered piano at a normal pitch range. As a PART parameter.
Press [EDIT]
Press a button 1-4 in a Performance, or 1-16 in a MULTI to select the PART
Press [F4] TONE
Press [SF1] TUNE
Here you can NOTE SHIFT the Part by semi-tones up or down as necessary. +12/-12 is an octave.