Press and hold shift. Click on the card and drag it from your hand to the library. Um... that's about it
Grave Defiler: drag cards from your library into game space. Put zombie into your hand (select and trturn to hand or just drag to hand). For the rest, hold shift and drag them to library.
Opt: go to "view top cards of library", and choose 1. If you would like to keep it, drag it to your hand. If not, hold shift and drag it to your library. Then click ok, and draw a card.
If there are anymore questions, feel free to ask me, I'm starting to know this program well