@Millie8, hopefully you have solved this dilemma by now, but for the future, you can go to settings on your computer and browser and opt to have your computer automatically remember passwords for various sites you regularly use. I'm in the same boat- I'd never be able to remember all the passwords I have for various sites. I also write mine down in a special place, hard copy.
Then, when you go to log-on to that site, the log in box will automatically fill in your user name and password, all you have to do is click Log-in.
There is usually a box that pops up on my computer sceen when I open a new account on a new site or create an alternate email address, for instance, that says "Would you like Firefox (or whatever browser you use) to remember this password?"