If you add a Yahoo account and don't immediately import the leagues, there's two ways around this:
1) On any device, go to https://league.footballguys.com, login and hit "Check for more leagues" under your Yahoo account. Import them, then switch back to the Draft Dominator app where they should then be available.
2) Add a new league manually (scroll past the fantasy host options to find this option) to bypass the Add Draft screen. Then, go to More > Edit All My Leagues, hit "Check for more leagues" under your Yahoo account, import them, then you can add a new draft into one of these Yahoo leagues.