Yes. Credits in your wallet are applied automatically at checkout, and each credit is worth $1.10 when you buy a challenge (10% saving).
Go to Payouts and click New challenge in your wallet (or use Start challenge from the menu).
Choose your challenge as usual and click Get Funded.
In the order summary you see a Credits line deducting their value. If they cover the whole price, the total is $0.00.
Accept the terms and click Redeem (or Pay for any remaining amount).
Example: a 7K 1-Step costs $61.75 with the current discount. It is paid with 56.14 credits (56.14 × $1.10 = $61.75).