RE: Splinterlands Quest Potions Worth It?

Up at the top right next to your username, click your DEC balance

Next, enter the amount you want to transfer and click Steem Engine Wallet.

Then click transfer out.

I just realized this was the opposite of what you were asking.

In order to get your DEC into the game you just send it from your Steem Engine wallet to @steemmonsters and it will be put into your game account.

Now wait a few seconds and your DEC will show up in your Steem-Engine wallet. :)