The Rule 5 Draft is on December 11th in Career Mode. When you first start Career Mode, click on Advance League. You will be brought to the next major date during the offseason. Continue clicking this until it says that the Rule 5 Draft is about to start. When it says this, click that you want to start the draft. Once the draft starts and it is your turn to pick, pick any player that you want. It is best to pick the player on top of the list because they are the best overall, but you can pick whoever you want. Once you draft one player, you will unlock the achievement and you can either continue until the end of the draft or simulate until the end.