You simply pay the cost in their upper-left corner, before doing what the text says and putting the card in your discard pile
Theres also The Nipton Lottery, which is a pretty unreliable but very silly boardwipe and creature-stealing spell that seems like a blast to cast
If the second ability triggers multiple times in the same turn, perhaps because there were multiple combats, you will be able to play that many additional lands
The box holds ten basic 'Jumpstart' style packs, two for each color, which newbies can slam together to form a complete 40 card deck
Crew 3 (Tap any number of creatures you control with total power 3 or more: This Vehicle becomes an artifact creature until end of turn.) Whenever this Vehicle becomes crewed, up to one other target Vehicle you control becomes an artifact creature until end of turn
The value of X is calculated only once, as Ouroboroid's ability resolves