You use the user ID and password you would normally use to log on to your own account when you do so at any other time. TurboTax does not have your bank log on information.
If you are referring to the import function inside TurboTax, I have only ever seen an option to import a W-2, and I have never successfully gotten that to work (as it relies upon my W2-issuing employer to support that feature). I have a handful of various types of 1099's, but I must go to each source to pull them down if I don't have a hard copy mailed to me. Doing so requires me to have a valid login userid on each in order to get an electronic version.
Again---if you normally engage in online banking or check on those accounts using the internet, the log in information to use in order to import anything from those financial institutions would be the log in that you normally use. There is not a "special" one for you to use with TurboTax. Some financial institutions are partnered with TT so that you can import your documents like 1099R's, 1099INT's, etc. If yours is one of them, you can choose it from the list on the screen. If it is not on the list then you enter the data manually.
If you are having trouble understanding this, contact customer support for further help.
To call TurboTax customer support
https://ttlc.intuit.com/questions/1899263-what-is-the-turbotax-phone-number
They are available from 5 a.m. to 5 p.m. Pacific time Monday - Friday