I am currently rank level 21 and all hero levels are 10 or above (except the Demon Hunter).
I was trying to import a deck i found online, and i get the notification that I have not unlocked wild mode yet, but I cant find answers anywhere. (all I see is people guessing).
I am new to the game (playing for about a week) so please don’t assume I know anything 
Oh, and I have tried to defeat the demon hunter in the prologue at least 10 times and I haven’t even come close. 
You need a wild card to unlock the wild mode.
Either you craft it or you just download the solo adventure in the link below and play the prologue to get a wild Legendary card for free.
The solo adventure is also for free.
Have fun 
Nice link.
It says you need to be rank 25 to use, but it looks like it works even at rank 40.
Wild used to be locked for players in the “new player ranks” that started at rank 50 and extended through to 26. Ranks 25 - 1 were considered “regular ranks”, and you needed to be at least 25 to unlock wild.
However, as of April the ranking systems were completely overhauled. The “regular ranks” are now silver, bronze, gold, diamond, and platinum (all from 10 to 1). And the “new player ranks” are now renamed to “apprentice ranks”, starting at 40 and ranging to 1.
I would have assumed that you had to be out of apprentice ranks (in other words, at Bronze 10 or better) to unlock Wild. Your response to the link posted by Kazakus makes me doubt that.
Either way, once you are (1) at the minimum level required to unlock Wild, and (2) in the possession of at least one card that is Wild-only, you can mark decks you create as “Wild”, at which point you can use all cards in them, and queue those decks up for play in Wild mode.
I hope this helps.
The shop item descriptions are still outdated “Requires Rank 25 or better” is the old rank system
I thought this was the case too.
Thank you. After I played, and won, the first round of KotFT, I received a legendary wild card. When I went to look at it in my collection, a popup stated I needed to be Bronze 10 to use it. Since I am currently level 21 apprentice, it seems I still have a way to go Thank you all for your help!
You’re an OG for this, i unlocked wild and got a free Guldan too
I’m happy for you.
That’s one of the best death knight cards.
Gul’dan is still seeing play.