Apple ID password
I don’t remember my Apple ID password. What do I do?
See -> If you can't connect or sign in to iCloud
If you can't connect or sign in to iCloud - Apple Support
Have you forgotten your password?, See -> Change your Apple ID password -> Change your Apple ID password - Apple Support
Then see this Apple article: What to do after you change your Apple ID or password
What to do after you change your Apple ID or password - Apple Support
BTW:
You are sign in here . . . with your Apple ID & Password.
Your Apple ID is the personal account you use with all Apple products and services. It includes the email address and password you use to sign in, as well as the contact, payment, and security details that you use with Apple.
You can’t merge multiple Apple ID accounts.
What happens when you use the same Apple ID & Password that you use to sign in here?
See -> Sign in with your Apple ID -> Sign in with your Apple ID - Apple Support