Setting up TouchID on Webpages previously NOT using autofill

I don't know how to ask this question...so here goes:

Been a MBP user for a long time. Just bought a new MBP with Touch ID. If I had previously signed into a webpage with autofill of username and password, then my TouchID works great. If I previously said to "NOT" use AutoFill (bank account, etc), now that I have a fingerprint ID, I'd like to use that. How do I set that particular webpage to now use Touch ID?