Looks like nominal is 12 V. Max for regulator is 26 V, but that probably exceeds Tj for
the regulator under load. You need to calculate load current, and do the thermal analysis
to make sure you do not exceed Tj, even though it does have internal thermal protection
and short circuit capability.
The power circuit shown in AN76530 provides provision to connect one of 3 sources -battery (VBAT), supply from DC adapter (PWR JACK) and voltage from another circuit (VIN). If you are using a single source, you don't have to connect D6 and D5.
You can either use a battery of 12V or build a unregulated power supply (~12V) (step down transformer -> bridge rectifier). For 5V regulator, you can use most commonly available IC LM7805.