You will be able to receive and claim some Coins from your in game Mailbox (tap on your profile in the upper left corner of the screen) and then select the Mailbox, or by completing various tasks in game.

You should have around 300 or more soon after you start playing the game if you follow all the quests, so do this and then head on to the Draft tab (bottom side of the screen) and select the Premium tab.

There you will be able to perform the very first draft, the Superstar Draft. There you will have to tap on the Pick 10 and pay 300 Coins for it, because that one will actually give you 11 drafts for the price of 10! So it's definitely super worth it.

Once you did that, you can then tap on the left or right arrow (either one, just tap once) and you will be able to do your GP Draft. The chances of getting super good S players from this are lower, but it costs GP so it's way easier to do than the Superstar Draft which costs Coins (premium currency).