I want to submit a druid subclass I created but the features by level do not match up. To fix this I'd like to add extra attack as a level 5 scaled feature to a feature obtained when picking the circle at level two. Does anyone have any insight on how to do this?

Need some clarity, you want to add Extra Attack (as in the general class feature at level 5)? or you want an extra attack specific to a subclass feature? But I will try to answer.

If you want to add the Extra Attack feature itself, you can do so by creating the subclass, save it, click "add a class feature", input the text, set the required level to 5, and save.

If you want an extra attack specific to a subclass feature, then you create the subclass, save it, create the subclass feature, save it, scroll to "class feature options", click on add an option, input the text, set the required level, and save.

I'm not sure what you are asking. Druids need features at level 2, 3 (for some reason), 6, 10, and 14. Not level 5. If you want to add extra attack, I recommend level 6.

I have extra attack added as a level 5 feature but it is not letting me submit (I'm guessing because Druids don't get a feature at level 5). What I'm trying to do is add it as a scaled feature to a level 2 ability starting at level 5. This would allow me to remove it as a level 5 feature so I can submit the subclass.

I don't think it is possible for a feature to add more features at higher level. You can increase number of uses and dice size at higher level, I think that is it.

You can still use a homebrew in your campaigns even without publishing it.