you can find the instructions for setting up an app password at:
https://www.sky.com/help/articles/getting-started-with-sky-yahoo-mail#need-a-hand
about 2/3 of the way down in the android section, though they seem to indicate that your sky.com pw should work. yahoo is making the change so it may be good to set up/use an app password.
their documentation shows the imap host as “imap.tools.sky.com” rather than just “imap.sky.com”, but they seem to resolve to the same ipnumber so it may not matter (unless they are using SNI).