Confused: new passwords on all devices

Tearing my hair out!! Having trouble synchronising passwords across devices. Is this a manual or (as I was lead to believe early in 2015 when I purchased this laptop) automatic thing. Need step by step instruction and a fast fix or am about to throw in the Apple towel. A load of confusion, multiple attempts - an not a newbie....but need to stop stressing and get a result. Do I call support? Does anyone have a link they could share? Even of relevant, helpful videos (I watched one before getting lost in detail). Even looking through threads today is like eating one mint too many. 🙂