How do I find my login information from my website profile and copy/paste it to my login entry on the app of this...website?
I need help I wanna use my same login as I did on the website but I can't remember what it was
It seems that you want to merge your accounts. You can do so very easily: just ask here, on Meta, for it to be done.
More info here:
I accidentally created two accounts; how do I merge them?
If you have two accounts that you would like to join together, please sign into either account, visit the contact form and select ‘I need to merge user profiles’. After you contact us, the Stack Exchange Team will reach out to verify that you own both accounts. If we can confirm your ownership, we will initiate a merge.
If you can't remember how to log in, go here and enter the email address you used to create the account you are trying to sign into.