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Would you mind explain how you did? I have Bitfinex account too, but I haven't done such things there because not sure how to do it...

Sure

When you are in Wallets, you will see you have an Exchange, Funding and Margin wallets, you need your coins/fiat in the Funding Wallet.

Then top left corner, click Funding, this will bring you to the funding area. Choose the coin/fiat you want to lend out and setup a funding offer.

if you won't figure it out , i'll might make a detailed guide.

Got it, I really appreciate.
Detailed guide may be a new post for your Steemit portfolio! If you decide to write about it, I would be glad to upvote it.