I need a manual/instruction, a beginners lesson book for Casio CTK-574 61 key keyboard, please.

A Casio Keyboard Service Centre is the best idea.

Casio Ctk-900 Service Manual - CTK900 - HelpOwl.com

https://www.helpowl.com > Casio > CTK900 > Research
Casio Ctk-900 Service Manual - CTK900 ... Get support for Casio CTK900 ... Our system has returned the following pages from the Casio CTK900 data we have on ...

Manual Casio CTK-900 (page 1 of 108) (English) - Libble.eu

https://www.libble.eu > ... > Casio > CTK-900
View and download the Manual of Casio CTK-900 Keyboard (page 1 of 108) (English). ... authorized CASIO Service Provider. AC Adaptor

http://www.usersmanualguide.com/manuals/casio/CTK-150%20CASTELLANO.pdf


http://www.usersmanualguide.com/manuals/casio/CTK-150%20CASTELLANO.pdf

If you turn it over, you will see the battery compartment. It runs on 6 AA batteries. Here's a link to the manual. Instructions are on page 13.
http://support.casio.com/pdf/008/ctk_496_700_e.pdf

http://support.casio.com/en/manual/manual.php?cid=008

http://support.casio.com/manuallist.php?rgn=1&cid=008
The link i have attached is a direct to Casio's website and their user manuals. i dont think the one your looking for is on the however, you might find a model very similar to yours to use as a reference.
is there a problem your having with the keyboard?

Get it here from Casio's website http://support.casio.com/manualfile.php?rgn=2&cid=008005005

Check for videos on YouTube. Also check for user's BLOGs for the Casio using Google. here usually isn't enough market for people to write 101 books as the technology and models change so fast.

Best way is to just dig in and try stuff and self-discovery results in learning stuff that sticks with you.

click here
Its available right off the casio website
enjoy
Sincerely,
Michael Scott

According to the manual for the 496, "All keyboard settings are returned to their initial defaults whenever keyboard power is turned back on after being turned off by operation of the Power/Mode switch or Auto Power Off.