See Passphrase, Not Password and Threats are not personal first.
All your accounts need to have secure (read: long) and unique passwords. It can be a struggle just to invent decent unique passwords for all your accounts, never mind remembering them. The answer is a password manager or vault. Web browsers have been offering to "remember" passwords for you forever but in the past, they stored your passwords in clear text where they could easily be stolen from your PC. Now password managers have their own online accounts (Firefox) or can be tied to your existing cloud accounts. Chrome and Android can store passwords in your Google account. The Apple world has iCloud accounts for iPhone and Mac. These are good basic solutions, but a better solution is a purpose built password vault like BitWarden, 1Password, or an add on to an existing security account like ProtonEmail or NordVPN.
If you are alone in your online presence, the basic managers from Google or Apple may be all you need. You just need to make sure your secure your cloud accounts and make sure you can use the manager everywhere you need a password. This may mean using a particular browser to have access to the manager. For example, if you have a Google account, you need to use Chrome on Windows, MacOS, and Linux. Your Android device comes with Chrome already.
The basics for all password vaults are the same:
You create your account with the password vault carefully. Excellent passphrase. Two factor authentication. Robust recovery procedures like setting up backup access with a friend. The passwords are only as secure as your access to the vault -- which also means if you do it right and you forget your vault password, you will never get them back.
You install the password vault on all your devices and browsers. Android and iPhone have apps, browsers have plugins. Some have stand alone applications for MacOS, Windows, and Linux. Some have web sites.
You move existing accounts to the vault, perhaps updating passwords as you go.
You let the vault generate all your passwords instead of inventing them yourself and saving them.
You stop worrying about looking up passwords or remembering them: visit a web site, the plugin automatically makes the username and password available.
You may need to cut and paste passwords for special cases like for applications instead of web sites.
I started with LastPass but was unhappy with the way they handled reporting a data breech they ad that exposed all customer vaults in their cloud backup system. I also learned that they were only encrypting the passwords and secrets, leaving my list of accounts and usernames in the clear to be stolen.
I am now using BitWarden. There are many other vaults with good reputations. I chose one that is cloud based so it is available to all my computers and devices and that allows for passwords to be shared with family members. In the past, I used PasswordSafe and manually synchronized the files.