At this time there is, unfortunately, no auto-draft support for Auction based leagues.
While this may change in the future, this feature doesn't exist right now for Auction leagues.
If you are running a Traditional style draft (non-Auction), you can turn on Auto-Draft by doing the following:
- Click on "TEAMS"
- Select the team you wish to edit to be "Auto-Draft"
- Click the "Auto-Draft' drop-down, and select "On"
- Click the green "Save Team" button.