Hi @devtoronto
Go to Settings (next tab), click on Disconnect and change the username. I highly advise against doing so - as this is a single login that will affect your Google Merchant and Google Ads login.
Instead, you should give that email address admin access to your (new) GA4 profile, click on the “Get Started” button and connect it.
Once you decided that this will be your admin (email) address, it should be used consistently across all your Google tools.