I can't get to the relevant link myself, as one needs to be signed into a Sky account to do so. However this would seem to help:
https://www.sky.com/help/articles/getting-started-with-sky-yahoo-mail
Under 'Mobile or tablet', click 'Android'.
Under 'Still can’t access your emails?', click 'Generate an app password'.
[NB: It might be best to sign into your Sky account BEFORE doing the above, so that the 'Generate an app password' link doesn't just lead you to a sign-in page, as it does for me].