How do you "tie" accounts together?

Let me try to be clear.  Let's say I have 5 websites that all use a domain username/password service account that's tied to me.  When I got to the website it prompts username/password and 1Password opens up when I put in the domain username/password, and it's saved.  I repeated his 4 more times to 4 different sites.

My domain password needs to be reset which makes me manually have to update all 5 sites.

I want 1Password to allow me to tell these 5 sites to use the username/password in a stored credential.  So when time comes to update that domain password the 5 sites automatically have the updated password to access it.