You will throw your bike in frustration more than once if you’re determined to learn how to manual!
Put you’re saddle down to start with. I think of it as a reverse ‘L’ shape. Pump your legs down and then straighten your arms forcing yourself backside behind your saddle – but not actually pulling on the handlebars
If you don’t use flats, start. The fear of looping out when running clipless will stop you putting in a good pump.
People always mention feathering the brake to help keep balance. But if you’re just starting out, I wouldn’t worry about.
Good luck, and you are right it’s pretty essential skill. If you can’t manual, you can’t bunny hop (properly), if you can’t bunny hop you can’t jump (properly)….